Quantum feedback in a non-resonant cavity QED system
Photon correlation measurements reveal the response of the conditional evolution of the cavity QED system to a novel quantum feedback protocol. A photodetection collapses the state of the system and triggers a feedback pulse with an adjustable delay and amplitude that alters the intensity driving the system. The conditional evolution of the system freezes into a new steady state where it resides until, after an amount of time determined by the experimenter, it re-equilibrates into the original steady state. We carry out a sensitivity analysis using a theoretical model with atomic detuning and make quantitative comparisons with measured results
Scheme for Quantum Entanglement Swapping on Cavity QED System
CHEN Chang-Yong; YU Yan
2006-01-01
We propose a scheme for realizing quantum entanglement swapping between the atoms in cavity QED.With only virtual excitation of the cavity during the interaction between the atoms and cavity, the scheme is insensitive to the cavity mode states and the cavity decay. The ideas can also be utilized for realizing entanglement swapping between the atomic levels in a single atom and the atomic levels in the Bell states and between the atomic levels in the Bell states and the atomic levels in the W states.
Quantum interference effects in a cavity QED system
We consider the effect of quantum interference on population distribution and photon statistics of a cavity field interacting with dressed states of a strongly driven three-level atom. We analyse three coupling configurations of the cavity field to the driven atom, with the cavity frequency tuned to the outer Rabi sideband, the inner Rabi sideband and the central frequency of the 'singly dressed' three-level atom. The quantum doubly dressed states for each configuration are identified and the population distribution and photon statistics are interpreted in terms of transitions among these dressed states and their populations. We find that the population distribution depends strongly on quantum interference and the cavity damping. For the cavity field tuned to the outer or inner Rabi sidebands the cavity damping induces transitions between the dressed states which are forbidden for the ordinary spontaneous emission. Moreover, we find that in the case of the cavity field coupled to the inner Rabi sideband the population distribution is almost Poissonian with a large average number of photons that can be controlled by quantum interference. This system can be considered as a one-atom dressed-state laser with controlled intensity
Stimulated photon emission and two-photon Raman scattering in a coupled-cavity QED system
Li, C.; Song, Z.
2016-01-01
We study the scattering problem of photon and polariton in a one-dimensional coupled-cavity system. Analytical approximate analysis and numerical simulation show that a photon can stimulate the photon emission from a polariton through polariton-photon collisions. This observation opens the possibility of photon-stimulated transition from insulating to radiative phase in a coupled-cavity QED system. Inversely, we also find that a polariton can be generated by a two-photon Raman scattering process. This paves the way towards single photon storage by the aid of atom-cavity interaction. PMID:26877252
QND Measurements in a Resonant Cavity-QED System
Chen, Zilong; Bohnet, Justin G.; Dai; Thompson, James K.
2010-03-01
We demonstrate QND measurements on an ensemble of 10^6 ^87Rb atoms. Quantum state-dependent populations are determined at the projection noise level by measurements of the collective Vacuum Rabi Splitting for the resonantly coupled atom-cavity system. The splitting is measured by simultaneously scanning the frequency of two probes across the two transmission resonances and phase coherently detecting the full IQ response of the reflected electric fields. Measurement back-action imposes AC Stark shifts on the atoms, resulting in a reduction of the Ramsey fringe contrast due to inhomogeneity in the probe-atom coupling. We show that the spin-echo sequences that will be needed to achieve atomic spin-squeezing on the Rb clock transition also strongly suppress these AC stark shifts. The remaining probe-induced decoherence is close to the fundamental limit imposed by free space scattering of the probe photons.
Photonic ququart logic assisted by the cavity-QED system
Luo, Ming-Xing; Deng, Yun; Li, Hui-Ran; Ma, Song-Ya
2015-08-01
Universal quantum logic gates are important elements for a quantum computer. In contrast to previous constructions of qubit systems, we investigate the possibility of ququart systems (four-dimensional states) dependent on two DOFs of photon systems. We propose some useful one-parameter four-dimensional quantum transformations for the construction of universal ququart logic gates. The interface between the spin of a photon and an electron spin confined in a quantum dot embedded in a microcavity is applied to build universal ququart logic gates on the photon system with two freedoms. Our elementary controlled-ququart gates cost no more than 8 CNOT gates in a qubit system, which is far less than the 104 CNOT gates required for a general four-qubit logic gate. The ququart logic is also used to generate useful hyperentanglements and hyperentanglement-assisted quantum error-correcting code, which may be available in modern physical technology.
Quantum state tomography via mutually unbiased measurements in driven cavity QED systems
Yuan, Hao; Zhou, Zheng-Wei; Guo, Guang-Can
2016-04-01
We present a feasible proposal for quantum tomography of qubit and qutrit states via mutually unbiased measurements in dispersively coupled driven cavity QED systems. We first show that measurements in the mutually unbiased bases (MUBs) are practically implemented by projecting the detected states onto the computational basis after performing appropriate unitary transformations. The measurement outcomes can then be determined by detecting the steady-state transmission spectra (SSTS) of the driven cavity. It is found that all the measurement outcomes for each MUB (i.e., all the diagonal elements of the density matrix of each detected state) can be read out directly from only one kind of SSTS. In this way, we numerically demonstrate that the exemplified qubit and qutrit states can be reconstructed with the fidelities 0.952 and 0.961, respectively. Our proposal could be straightforwardly extended to other high-dimensional quantum systems provided that their MUBs exist.
Phase-selective reversible quantum decoherence in cavity QED experiment
Filip, Radim
2001-01-01
New feasible cavity QED experiment is proposed to analyse reversible quantum decoherence in consequence of quantum complementarity and entanglement. Utilizing the phase selective manipulations with enviroment, it is demonstrated how the complementarity particularly induces a preservation of visibility, whereas quantum decoherence is more progressive due to pronounced entanglement between system and enviroment. This effect can be directly observed using the proposed cavity QED measurements.
Feedback in a cavity QED system for control of quantum beats
Cimmarusti A.D.
2013-08-01
Full Text Available Conditional measurements on the undriven mode of a two-mode cavity QED system prepare a coherent superposition of ground states which generate quantum beats. The continuous system drive induces decoherence through the phase interruptions from Rayleigh scattering, which manifests as a decrease of the beat amplitude and an increase of the frequency of oscillation. We report recent experiments that implement a simple feedback mechanism to protect the quantum beat. We continuously drive the system until a photon is detected, heralding the presence of a coherent superposition. We then turn off the drive and let the superposition evolve in the dark, protecting it against decoherence. At a later time we reinstate the drive to measure the amplitude, phase, and frequency of the beats. The amplitude can increase by more than fifty percent, while the frequency is unchanged by the feedback.
Mass renormalization in cavity QED
We show that the presence of a background medium and a boundary surface or surfaces in cavity QED produces no change in the energy shift of a free charged particle due to its coupling to the fluctuating electromagnetic field of the vacuum. This clarifies that the electromagnetic and the observed mass of the charged particle are not affected by the modification of the field of the vacuum. The calculations are nonrelativistic and restricted to the dipole approximation but are otherwise based on the general requirements of causality.
Cavity QED experiments with ion Coulomb crystals
Herskind, Peter Fønss; Dantan, Aurélien; Marler, Joan; Albert, Magnus; Drewsen, Michael
Cavity QED experimental results demonstrating collective strong coupling between ensembles of atomic ions cooled into Coulomb crystals and optical cavity fields have been achieved. Collective Zeeman coherence times of milliseconds have furthermore been obtained.......Cavity QED experimental results demonstrating collective strong coupling between ensembles of atomic ions cooled into Coulomb crystals and optical cavity fields have been achieved. Collective Zeeman coherence times of milliseconds have furthermore been obtained....
Generation of hybrid four-qubit entangled decoherence-free states assisted by the cavity-QED system
Zhou, You-Sheng; Li, Xian; Deng, Yun; Li, Hui-Ran; Luo, Ming-Xing
2016-05-01
We propose three effective protocols to generate four-qubit entangled decoherence-free states assisted by the cavity-QED system. These schemes are based on optical selection rules realized with a single electron charged self-assembled GaAs/InAs quantum dot in a micropillar resonator. Compared with previous photonic protocols, the first scheme is to replace the entangled-state resources with much simpler single-photon resources and has a deterministic success probability. Moreover, the cavity-QED system may be used to generate four-spin entangled decoherence-free states and hybrid four-qubit of spin-photon entangled decoherence-free states. These states may be applied up to different requirements because of different superiorities of photons and spins. All schemes may be implemented with current physical technologies.
A Position-Dependent Two-Atom Entanglement in Real-Time Cavity QED System
GUO Yan-Qing; CAO Hai-Jing; SONG He-Shan
2007-01-01
We study a special two-atom entanglement case in assumed cavity QED experiment in which only one atom effectively exchanges a single photon with a cavity mode. We compute two-atom entanglement under position-dependent atomic resonant dipole-dipole interaction (RDDI) for large interatomic separation limit. We show that the RDDI, even that which is much smaller than the maximal atomic Rabi frequency, can induce distinct diatom entanglement. The peak entanglement reaches a maximum when RDDI strength can compare with the Rabi frequency of an atom.
Observing different quantum trajectories in cavity QED
Santos, Marcelo França
2011-01-01
The experimental observation of quantum jumps is an example of single open quantum systems that, when monitored, evolve in terms of stochastic trajectories conditioned on measurements results. Here we present a proposal that allows the experimental observation of a much larger class of quantum trajectories in cavity QED systems. In particular, our scheme allows for the monitoring of engineered thermal baths that are crucial for recent proposals for probing entanglement decay and also for entanglement protection. The scheme relies on the interaction of a three-level atom and a cavity mode that interchangeably play the roles of system and probe. If the atom is detected the evolution of the cavity fields follows quantum trajectories and vice-versa.
Simulating Topological Effects with Photons in Coupled QED Cavity Arrays
Noh, Changsuk; Angelakis, Dimitris G.
2014-01-01
We provide a pedagogical account of an early proposal realizing fractional quantum Hall effect (FQHE) using coupled quantum electrodynamics (QED) cavity arrays (CQCAs). We start with a brief introduction on the basics of quantum Hall effects and then review the early proposals in the simulation of spin-models and fractional quantum Hall (FQH) physics with photons in coupled atom-cavity arrays. We calculate the energy gap and the overlap between the ground state of the system and the corresponding Laughlin wavefunction to analyze the FQH physics arising in the system and discuss possibilities to reach the ground state using adiabatic methods used in Cavity QED.
Cavity QED with atom chips and micro-resonators
Lev, Benjamin; Barclay, Paul; Kerckhoff, Joseph; Painter, Oskar; Mabuchi, Hideo
2006-05-01
Cavity QED provides a rich experimental setting for quantum information processing, both in the implementation of quantum logic gates and in the development of quantum networks. Moreover, studies of cavity QED will help elucidate the dynamics of continuously observed open quantum systems with quantum- limited feedback. To achieve these goals in cavity QED, a neutral atom must be tightly confined inside a high-finesse cavity with small mode volume for long periods of time. Microfabricated wires on a substrate---known as an atom chip---can create sufficiently high-curvature magnetic potentials to trap atoms in the Lamb- Dicke regime. The integration of micro-resonators, such as microdisks and photonic bandgap cavities, with atom chips forms a robust and scalable system capable of probing the strong- coupling regime of cavity QED with magnetically trapped atoms. We have recently built an atom-cavity chip utilizing a fiber taper coupled microdisk resonator. This device combines laser cooling and trapping of neutral atoms with magnetic microtraps and waveguides to deliver cold atoms to the small mode volume of the high-Q cavity. We will relate our progress toward detecting single atoms with this device.
We propose a method for implementing the Grover search algorithm directly in a database containing any number of items based on multi-level systems. Compared with the searching procedure in the database with qubits encoding, our modified algorithm needs fewer iteration steps to find the marked item and uses the carriers of the information more economically. Furthermore, we illustrate how to realize our idea in cavity QED using Zeeman's level structure of atoms. And the numerical simulation under the influence of the cavity and atom decays shows that the scheme could be achieved efficiently within current state-of-the-art technology. -- Highlights: ► A modified Grover algorithm is proposed for searching in an arbitrary dimensional Hilbert space. ► Our modified algorithm requires fewer iteration steps to find the marked item. ► The proposed method uses the carriers of the information more economically. ► A scheme for a six-item Grover search in cavity QED is proposed. ► Numerical simulation under decays shows that the scheme can be achieved with enough fidelity.
Quantum signalling in cavity QED
Jonsson, Robert H.; Martin-Martinez, Eduardo; Kempf, Achim
2013-01-01
We consider quantum signalling between two-level quantum systems in a cavity, in the pertubative regime of the earliest possible arrival times of the signal. We present two main results: First we find that, perhaps surprisingly, the analogue of amplitude modulated signalling (Alice using her energy eigenstates |g>, |e>, as in the Fermi problem) is generally sub-optimal for communication. Namely, e.g., phase modulated signalling (Alice using, e.g., |+>,|e>-states) overcomes the quantum noise a...
Scheme for Implementation of Quantum Game in Cavity QED
ZHANG Li-Chun; CAO Shu-Ai; WU Yue-Qin; FANG Mao-Fa; LI Huai-Fan; ZHENG Xiao-Juan; ZHAO Ren; WANG Xin-Wen; LI Ze-Hua
2008-01-01
We propose an experimentally feasible scheme to implement two-player quantum game in cavity quantum electrodynamics (QED). During the process, the cavity is only virtually excited, thus our scheme is insensitive to the cavity field states and cavity decay. The scheme can be realized in the range of current cavity QED techniques.
Scheme for Implementation of Quantum Game in Cavity QED
We propose an experimentally feasible scheme to implement two-player quantum game in cavity quantum electrodynamics (QED). During the process, the cavity is only virtually excited, thus our scheme is insensitive to the cavity field states and cavity decay. The scheme can be realized in the range of current cavity QED techniques.
Generation of Cluster States in Cavity QED
ZHOU Yan-Li; YANG Li-Jia; DAI Hong-Yi
2007-01-01
We propose two schemes for the generation of cluster states in the context of cavity quantum electrodynamics (QED).In the first scheme,we prepare multi-cavity cluster states with information encoded in the coherent states.The second scheme is to generate multi-atom cluster states,where qubits are represented by the states of cascade Rydberg atoms.Both the schemes are based on the atom-cavity interaction and the atomic spontaneous radiation can be effciently reduced since the cavity frequency is largely detuned from the atomic transition frequency.
Single ion cavity QED experiments
Full text: We have set up a spherical Paul trap for a storing a single Ca+ ion placed in the center of a high finesse near confocal resonator. We report on experiments demonstrating the coupling of the narrow S1/2-D5/2 transition to the cavity internal light field. Due to the coupling, the ion acts as sensitive probe for the cavity internal field. We are able to map the field distribution by measuring the excitation probability. Scanning the cavity over the resonance imprints a Doppler frequency shift on the cavity field which leads to a spectral shift and a asymmetric broadening of the S-D transition. (author)
Theoretical analysis of quantum game in cavity QED
Recent years, several ways of implementing quantum games in different physical systems have been presented. In this paper, we perform a theoretical analysis of an experimentally feasible way to implement a two player quantum game in cavity quantum electrodynamic(QED). In the scheme, the atoms interact simultaneously with a highly detuned cavity mode with the assistance of a classical field. So the scheme is insensitive to the influence from the cavity decay and the thermal field, and it does not require the cavity to remain in the vacuum state throughout the procedure. (general)
Quantum-to-Classical Transition in Cavity Quantum Electrodynamics (QED)
Fink, J M; Studer, P; Bishop, Lev S; Baur, M; Bianchetti, R; Bozyigit, D; Lang, C; Filipp, S; Leek, P J; Wallraff, A
2010-01-01
The quantum properties of electromagnetic, mechanical or any other type of harmonic oscillator can be revealed by investigating its strong coherent coupling to a single quantum two level system in an approach known as cavity QED. At temperatures much lower than the characteristic energy level spacing the observation of vacuum Rabi oscillations or mode splittings with one or a few quanta asserts the quantum nature of the system. Here, we study how the classical response of a quantum cavity QED system emerges when its thermal occupation -- or effective temperature -- is raised gradually over 5 orders of magnitude. In this way we explore in detail the continuous cross-over from a quantum response to a classical response in the spirit of Bohr's correspondence principle. We also demonstrate how to extract effective cavity field temperatures from both spectroscopic and time-resolved vacuum Rabi measurements.
Sensitive Detection of Individual Neutral Atoms in a Strong Coupling Cavity QED System
ZHANG Peng-Fei; ZHANG Yu-Chi; LI Gang; DU Jin-Jin; ZHANG Yan-Feng; GUO Yan-Qiang; WANG Jun-Min; ZHANG Tian-Cai; LI Wei-Dong
2011-01-01
We experimentally demonstrate real-time detection of individual cesium atoms by using a high-finesse optical micro-cavity in a strong coupling regime.A cloud of cesium atoms is trapped in a magneto-optical trap positioned at 5 mm above the micro-cavity center.The atoms fall down freely in gravitation after shutting off the magnetooptical trap and pass through the cavity.The cavity transmission is strongly affected by the atoms in the cavity, which enables the micro-cavity to sense the atoms individually.We detect the single atom transits either in the resonance or various detunings.The single atom vacuum-Rabi splitting is directly measured to be Ω = 2π × 23.9 MHz.The average duration of atom-cavity coupling of about 110μs is obtained according to the probability distribution of the atom transits.%@@ We experimentally demonstrate real-time detection of individual cesium atoms by using a high-finesse optical micro-cavity in a strong coupling regime.A cloud of cesium atoms is trapped in a magneto-optical trap positioned at 5mm above the micro-cavity center.The atoms fall down freely in gravitation after shutting off the magnetooptical trap and pass through the cavity.The cavity transmission is strongly affected by the atoms in the cavity, which enables the micro-cavity to sense the atoms individually.We detect the single atom transits either in the resonance or various detunings.The single atom vacuum-Rabi splitting is directly measured to be Ω＝2π×23.9 MHz.The average duration of atom-cavity coupling of about 110μs is obtained according to the probability distribution of the atom transits.
Scheme for implementing quantum secret sharing via cavity QED
Chen Zhi-Hua; Lin Xiu-Min
2005-01-01
An experimentally feasible scheme for implementing quantum secret sharing via cavity quantum electrodynamics (QED) is proposed. The scheme requires the large detuning of the cavity field from the atomic transition, the cavity is only virtually excited, thus the requirement on the quality factor of the cavity is greatly loosened.
High-Q 3D coaxial resonators for cavity QED
Yoon, Taekwan; Owens, John C.; Naik, Ravi; Lachapelle, Aman; Ma, Ruichao; Simon, Jonathan; Schuster, David I.
Three-dimensional microwave resonators provide an alternative approach to transmission-line resonators used in most current circuit QED experiments. Their large mode volume greatly reduces the surface dielectric losses that limits the coherence of superconducting circuits, and the well-isolated and controlled cavity modes further suppress coupling to the environment. In this work, we focus on unibody 3D coaxial cavities which are only evanescently coupled and free from losses due to metal-metal interfaces, allowing us to reach extremely high quality-factors. We achieve quality-factor of up to 170 million using 4N6 Aluminum at superconducting temperatures, corresponding to an energy ringdown time of ~4ms. We extend our methods to other materials including Niobium, NbTi, and copper coated with Tin-Lead solder. These cavities can be further explored to study their properties under magnetic field or upon coupling to superconducting Josephson junction qubits, e.g. 3D transmon qubits. Such 3D cavity QED system can be used for quantum information applications, or quantum simulation in coupled cavity arrays.
Distillation of bi-partite entanglement from W state with cavity QED
Deng Li; Chen Ai-Xi; Chen De-Hai; Huang Ke-Lin
2008-01-01
Following the theoretical protocol described by Fortescue and Lo [Fortescue B and Lo H K 2007 Phys. Rev. Lett. 98 260501], we present a scheme in which one can distill maximally entangled bi-partite states from a tri-partite W state with cavity QED. Our scheme enables the concrete physical system to realize its protocol. In our scheme, the rate distillation also asymptotically approaches one. Based on the present cavity QED techniques, we discuss the experimental feasibility.
A Cavity QED Implementation of Deutsch-Jozsa Algorithm
Guerra, E. S.
2004-01-01
The Deutsch-Jozsa algorithm is a generalization of the Deutsch algorithm which was the first algorithm written. We present schemes to implement the Deutsch algorithm and the Deutsch-Jozsa algorithm via cavity QED.
Phase-factor-dependent symmetries and quantum phases in a three-level cavity QED system
Fan, Jingtao; Yu, Lixian; Chen, Gang; Jia, Suotang
2016-05-01
Unlike conventional two-level particles, three-level particles may support some unitary-invariant phase factors when they interact coherently with a single-mode quantized light field. To gain a better understanding of light-matter interaction, it is thus necessary to explore the phase-factor-dependent physics in such a system. In this report, we consider the collective interaction between degenerate V-type three-level particles and a single-mode quantized light field, whose different components are labeled by different phase factors. We mainly establish an important relation between the phase factors and the symmetry or symmetry-broken physics. Specifically, we find that the phase factors affect dramatically the system symmetry. When these symmetries are breaking separately, rich quantum phases emerge. Finally, we propose a possible scheme to experimentally probe the predicted physics of our model. Our work provides a way to explore phase-factor-induced nontrivial physics by introducing additional particle levels.
Phase-factor-dependent symmetries and quantum phases in a three-level cavity QED system
Fan, Jingtao; Yu, Lixian; Chen, Gang; Jia, Suotang
2016-01-01
Unlike conventional two-level particles, three-level particles may support some unitary-invariant phase factors when they interact coherently with a single-mode quantized light field. To gain a better understanding of light-matter interaction, it is thus necessary to explore the phase-factor-dependent physics in such a system. In this report, we consider the collective interaction between degenerate V-type three-level particles and a single-mode quantized light field, whose different components are labeled by different phase factors. We mainly establish an important relation between the phase factors and the symmetry or symmetry-broken physics. Specifically, we find that the phase factors affect dramatically the system symmetry. When these symmetries are breaking separately, rich quantum phases emerge. Finally, we propose a possible scheme to experimentally probe the predicted physics of our model. Our work provides a way to explore phase-factor-induced nontrivial physics by introducing additional particle levels. PMID:27139573
Single atoms on demand for cavity QED experiments
Cavity quantum electrodynamics (cavity QED) describes electromagnetic fields in a confined space and the radiative properties of atoms in such fields. The simplest example of such system is a single atom interacting with one mode of a high-finesse resonator. Besides observation and exploration of fundamental quantum mechanical effects, this system bears a high potential for applications quantum information science such as, e.g., quantum logic gates, quantum communication and quantum teleportation. In this thesis I present an experiment on the deterministic coupling of a single neutral atom to the mode of a high-finesse optical resonator. In Chapter 1 I describe our basic techniques for trapping and observing single cesium atoms. As a source of single atoms we use a high-gradient magneto-optical trap, which captures the atoms from background gas in a vacuum chamber and cools them down to millikelvin temperatures. The atoms are then transferred without loss into a standing-wave dipole trap, which provides a conservative potential required for experiments on atomic coherence such as quantum information processing and metrology on trapped atoms. Moreover, shifting the standing-wave pattern allows us to deterministically transport the atoms (Chapter 2). In combination with nondestructive fluorescence imaging of individual trapped atoms, this enables us to control their position with submicrometer precision over several millimeters along the dipole trap. The cavity QED system can distinctly display quantum behaviour in the so-called strong coupling regime, i.e., when the coherent atom-cavity coupling rate dominates dissipation in the system. This sets the main requirements on the resonator's properties: small mode volume and high finesse. Chapter 3 is devoted to the manufacturing, assembling, and testing of an ultra-high finesse optical Fabry-Perot resonator, stabilized to the atomic transition. In Chapter 4 I present the transportation of single atoms into the cavity
Single atoms on demand for cavity QED experiments
Dotsenko, I.
2007-09-06
Cavity quantum electrodynamics (cavity QED) describes electromagnetic fields in a confined space and the radiative properties of atoms in such fields. The simplest example of such system is a single atom interacting with one mode of a high-finesse resonator. Besides observation and exploration of fundamental quantum mechanical effects, this system bears a high potential for applications quantum information science such as, e.g., quantum logic gates, quantum communication and quantum teleportation. In this thesis I present an experiment on the deterministic coupling of a single neutral atom to the mode of a high-finesse optical resonator. In Chapter 1 I describe our basic techniques for trapping and observing single cesium atoms. As a source of single atoms we use a high-gradient magneto-optical trap, which captures the atoms from background gas in a vacuum chamber and cools them down to millikelvin temperatures. The atoms are then transferred without loss into a standing-wave dipole trap, which provides a conservative potential required for experiments on atomic coherence such as quantum information processing and metrology on trapped atoms. Moreover, shifting the standing-wave pattern allows us to deterministically transport the atoms (Chapter 2). In combination with nondestructive fluorescence imaging of individual trapped atoms, this enables us to control their position with submicrometer precision over several millimeters along the dipole trap. The cavity QED system can distinctly display quantum behaviour in the so-called strong coupling regime, i.e., when the coherent atom-cavity coupling rate dominates dissipation in the system. This sets the main requirements on the resonator's properties: small mode volume and high finesse. Chapter 3 is devoted to the manufacturing, assembling, and testing of an ultra-high finesse optical Fabry-Perot resonator, stabilized to the atomic transition. In Chapter 4 I present the transportation of single atoms into the
Non-markovian effects in semiconductor cavity QED: Role of phonon-mediated processes
Nielsen, Per Kær; Nielsen, Torben Roland; Lodahl, Peter;
We show theoretically that the non-Markovian nature of the carrier-phonon interaction influences the dynamical properties of a semiconductor cavity QED system considerably, leading to asymmetries with respect to detuning in carrier lifetimes. This pronounced phonon effect originates from the pola...... polaritonic quasi-particle nature of the carrier-photon system interacting with the phonon reservoir.......We show theoretically that the non-Markovian nature of the carrier-phonon interaction influences the dynamical properties of a semiconductor cavity QED system considerably, leading to asymmetries with respect to detuning in carrier lifetimes. This pronounced phonon effect originates from the...
Protocol for multi-party superdense coding by using multi-atom in cavity QED
Tan Jia; Fang Mao-Fa
2006-01-01
We present a protocol for multi-party superdense coding by using multi-atom in cavity quantum electrodynamics (QED). It is shown that, with a highly detuned cavity mode and a strong driving field, the protocol is insensitive to both cavity decay and thermal field. It is even certain to identify GHZ states via detecting the atomic states. Therefore we can realize the quantum dense coding in a simple way in the multiparty system.
Atomic teleportation via cavity QED and position measurements: Efficiency analysis
Tumminello, M.; Ciccarello, F.
2008-07-01
We have recently presented a novel protocol to teleport an unknown atomic state via cavity QED and position measurements. Here, after a brief review of our scheme, we provide a quantitative study of its efficiency. This is accomplished by an explicit description of the measurement process that allows us to derive the fidelity with respect to the atomic internal state to be teleported.
Scheme for Implementing Quantum Cloning Restoring Machine in Cavity QED
YU Long-Bao; ZHANG Wen-Hai; YE Liu
2007-01-01
We propose an experimentally feasible scheme for implementing quantum restoring machine of the optimal universal 1 → 2 quanturn cloning machine in the context of cavity QED.In our scheme,two atoms (the clones) simultaneously interact with a cavity field,and meanwhile they are driven by a classical field.Then an arbitrary unknown input state can be restored in the ancilla by applying appropriate unitary local operation.
Generation of four-photon W state via cavity QED
Zhong Zhi-Rong
2008-01-01
This paper proposes an alternative scheme for generating four-photon W state via cavity QED.The scheme bases on the resonant interaction of a A-type three level atom with two bimodal cavities.The detection of atom collapses the cavity to the desired state.Comparing with previous schemes,the advantage of this scheme is that the interaction time can be greatly shortened since it uses the resonant interaction between atom and cavities.Moreover,the proposed scheme is more experimentally feasible than the previous ones.
Strong-Driving-Assisted Probabilistic State Preparation in Cavity QED
YANG Zhen-Biao
2006-01-01
An alternative scheme is proposed for preparing the superpositions of coherent states with controllable weighting factors along a straight line for a cavity field. The scheme is based on the interaction of a single-mode cavity field with a resonant two-level atom driven by a strong classical field. It is in contrast to the previous methods used in cavity QED of injecting a coherent state into a cavity via a microwave source. In the scheme, the interaction between the cavity mode and atoms is fully resonant, thus the required interaction time is greatly shortened. Moreover, the present scheme requires smaller numbers of operations. In view of decoherence, a reduction of interaction time and numbers of operations for the state preparation is very important for experimental implementation of quantum state engineering.
Quantum networks based on cavity QED
Ritter, Stephan; Bochmann, Joerg; Figueroa, Eden; Hahn, Carolin; Kalb, Norbert; Muecke, Martin; Neuzner, Andreas; Noelleke, Christian; Reiserer, Andreas; Uphoff, Manuel; Rempe, Gerhard [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany)
2014-07-01
Quantum repeaters require an efficient interface between stationary quantum memories and flying photons. Single atoms in optical cavities are ideally suited as universal quantum network nodes that are capable of sending, storing, retrieving, and even processing quantum information. We demonstrate this by presenting an elementary version of a quantum network based on two identical nodes in remote, independent laboratories. The reversible exchange of quantum information and the creation of remote entanglement are achieved by exchange of a single photon. Quantum teleportation is implemented using a time-resolved photonic Bell-state measurement. Quantum control over all degrees of freedom of the single atom also allows for the nondestructive detection of flying photons and the implementation of a quantum gate between the spin state of the atom and the polarization of a photon upon its reflection from the cavity. Our approach to quantum networking offers a clear perspective for scalability and provides the essential components for the realization of a quantum repeater.
Cavity QED Detection of Interfering Matter Waves
Bourdel, T; Donner, T.; Ritter, S; Öttl, A.; Köhl, M.; Esslinger, T.
2005-01-01
We observe the build-up of a matter wave interference pattern from single atom detection events in a double-slit experiment. The interference arises from two overlapping atom laser beams extracted from a Rubidium Bose-Einstein condensate. Our detector is a high-finesse optical cavity which realizes the quantum measurement of the presence of an atom and thereby projects delocalized atoms into a state with zero or one atom in the resonator. The experiment reveals simultaneously the granular and...
Cavity QED on a nanofiber using a composite photonic crystal cavity
Yalla, Ramachandrarao; Nayak, Kali P; Hakuta, Kohzo
2014-01-01
We demonstrate cavity QED conditions in the Purcell regime for single quantum emitters on the surface of an optical nanofiber. The cavity is formed by combining an optical nanofiber and a nanofabricated grating to create a composite photonic crystal cavity. Using this technique, significant enhancement of the spontaneous emission rate into the nanofiber guided modes is observed for single quantum dots. Our results pave the way for enhanced on-fiber light-matter interfaces with clear applications to quantum networks.
Efficient atomic quantum memory for photonic qubits in cavity QED
Yamada, H; Yamada, Hiroyuki; Yamamoto, Katsuji
2007-01-01
We investigate a scheme of atomic quantum memory to store photonic qubits of polarization in cavity QED. It is observed that the quantum-state swapping between a single-photon pulse and a $ \\Lambda $-type atom can be made via scattering in an optical cavity [T. W. Chen, C. K. Law, P. T. Leung, Phys. Rev. A {\\bf 69} (2004) 063810]. This swapping operates limitedly in the strong coupling regime for $ \\Lambda $-type atoms with equal dipole couplings. We extend this scheme in cavity QED to present a more feasible and efficient method for quantum memory combined with projective measurement. This method works without requiring such a condition on the dipole couplings. The fidelity is significantly higher than that of the swapping, and even in the moderate coupling regime it reaches almost unity by narrowing sufficiently the photon-pulse spectrum. This high performance is rather unaffected by the atomic loss, cavity leakage or detunings, while a trade-off is paid in the success probability for projective measurement...
Transformation of bipartite non-maximally entangled states into a tripartiteWstate in cavity QED
ZANG XUE-PING; YANG MING; DU CHAO-QUN; WANG MIN; FANG SHU-DONG; CAO ZHUO-LIANG
2016-05-01
We present two schemes for transforming bipartite non-maximally entangled states into a W state in cavity QED system, by using highly detuned interactions and the resonant interactions between two-level atoms and a single-mode cavity field. A tri-atom W state can be generated by adjusting the interaction times between atoms and the cavity mode. These schemes demonstrate that two bipartite non-maximally entangled states can be merged into a maximally entangled W state. So the scheme can, in some sense, be regarded as an entanglement concentration process. The experimental feasibility of the schemes is also discussed.
Quantum repeater based on cavity QED evolutions and coherent light
Gonţa, Denis; van Loock, Peter
2016-05-01
In the framework of cavity QED, we propose a quantum repeater scheme that uses coherent light and chains of atoms coupled to optical cavities. In contrast to conventional repeater schemes, in our scheme there is no need for an explicit use of two-qubit quantum logical gates by exploiting solely the cavity QED evolution. In our previous work (Gonta and van Loock in Phys Rev A 88:052308, 2013), we already proposed a quantum repeater in which the entanglement between two neighboring repeater nodes was distributed using controlled displacements of input coherent light, while the produced low-fidelity entangled pairs were purified using ancillary (four-partite) entangled states. In the present work, the entanglement distribution is realized using a sequence of controlled phase shifts and displacements of input coherent light. Compared to previous coherent-state-based distribution schemes for two-qubit entanglement, our scheme here relies only upon a simple discrimination of two coherent states with opposite signs, which can be performed in a quantum mechanically optimal fashion via a beam splitter and two on-off detectors. For the entanglement purification, we employ a method that avoids the use of extra entangled ancilla states. Our repeater scheme exhibits reasonable fidelities and repeater rates providing an attractive platform for long-distance quantum communication.
Observation of Cavity QED in thick dielectric films
Sarabi, Bahman; Ramanayaka, A. N.; Gladchenko, S.; Stoutimore, M. J. A.; Khalil, M. S.; Osborn, K. D.
2013-03-01
Cavity QED in amorphous dielectrics is investigated by measuring five linear superconducting resonators with thick dielectric films and capacitor volumes ranging from 80 μm3 to 5000 μm3. In the smallest volume dielectrics we observe additional resonances which may be explained by CQED, despite the dielectric volume which is many orders of magnitude larger than Josephson junction barrier volumes. In addition to the volume dependence of the CQED resonances, we will report on the stability of the resonances in time and the phase noise. This research allows new fundamental studies on TLS phenomena in meso-volume amorphous dielectrics.
Quantum Logic Network for Cloning a State Near a Given One Based on Cavity QED
ZHANG Da-Wei; SHAO Xiao-Qiang; ZHU Ai-Dong
2008-01-01
A quantum logic network is constructed to simulate a cloning machine which copies states near a given one. Meanwhile, a scheme for implementing this cloning network based on the technique of cavity quantum electrody-namics (QED) is presented. It is easy to implement this network of cloning machine in the framework of cavity QED and feasible in the experiment.
Quantum Logic Network for Cloning a State Near a Given One Based on Cavity QED
A quantum logic network is constructed to simulate a cloning machine which copies states near a given one. Meanwhile, a scheme for implementing this cloning network based on the technique of cavity quantum electrodynamics (QED) is presented. It is easy to implement this network of cloning machine in the framework of cavity QED and feasible in the experiment. (general)
Cavity-QED models of switches for attojoule-scale nanophotonic logic
Quantum optical input-output models are described for a class of optical switches based on cavity quantum electrodynamics (QED) with a single multilevel atom (or comparable bound system of charges) coupled simultaneously to several resonant field modes. A recent limit theorem for quantum stochastic differential equations is used to show that such models converge to a simple scattering matrix in a type of strong-coupling limit that seems natural for nanophotonic systems. Numerical integration is used to show that the behavior of the prelimit model approximates that of the simple scattering matrix in a realistic regime for the physical parameters and that it is possible in the proposed cavity-QED configuration for low-power optical signals to switch higher-power signals at attojoule energy scales.
We investigate a two-level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of the atom and cavity field as the time turns to infinity. We also find that the stationary quantum discord can be increased by applying a classical driving field. Furthermore, we explore the quantum discord dynamics of two identical non-interacting two-level atoms independently interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence. Results show that the quantum discord between two atoms is more robust than entanglement under phase decoherence and the classical driving field can help to improve the amount of quantum discord of the two atoms. (general)
Transferring a cavity field entangled state in cavity QED
Ye Liu [Anhui Key Laboratory of Information Material and Devices, School of Physics and Material Science, Anhui University, Hefei 230039 (China); Guo Guangcan [Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026 (China)
2005-08-01
We propose a scheme for transferring an entanglement of zero- and one-photon states from one cavity to another. The scheme, which has 100% success probability, is mainly based on a two-mode cavity dispersively interacting with a three-level atom in the {lambda} configuration and does not involve Bell-state measurement. This scheme can also be used to teleport an unknown atomic state.
Quantum-trajectory simulations of a two-level atom cascaded to a cavity QED laser
We use the quantum theory of cascaded open systems to calculate the transmitted photon flux for a weak beam of photons from a cavity QED laser strongly focused onto a single, resonant two-state atom in the narrow-bandwidth limit. We study the dependence of the transmitted flux on the quantum statistics of the incident light. Both bunched and antibunched light generated by the microlaser are considered as input. Working within and outside the semiclassical perturbative regime, we explicitly demonstrate that the normalized transmitted photon flux may coincide with the second-order correlation function of the incident bunched light, but not for incident antibunched light both of which are generated by a cavity QED laser. Interestingly, the thresholdless cavity QED laser is ideal for investigating statistical saturation effects by virtue of its small system size and the large quantum fluctuations accompanying it. It has the advantage of characterizing to a certain extent the quantum noise responsible for the statistical saturation. One can also easily vary the degree of antibunching of the incident light by manipulating the pumping rate of the laser
Nonprobabilistic teleportation of field state via cavity QED
De Carvalho, Carlos Renato; Guerra, Emerson S.; Jalbert, Ginette; Garreau, Jean Claude
2007-01-01
International audience In this article we discuss a teleportation scheme of coherent states of cavity field. The experimental realization proposed makes use of cavity quatum electrodynamics involving the interaction of Rydberg atoms with micromaser and Ramsey cavities. In our scheme the Ramsey cavities and the atoms play the role of auxiliary systems used to teleport the state from a micromaser cavity to another. We show that, even if the correct atomic detection fails in the first trials,...
Quantum optics and cavity QED with quantum dots in photonic crystals
Vuckovic, Jelena
2014-01-01
This chapter will primarily focus on the studies of quantum optics with semiconductor, epitaxially grown quantum dots embedded in photonic crystal cavities. We will start by giving brief introductions into photonic crystals and quantum dots, then proceed with the introduction to cavity quantum electrodynamics (QED) effects, with a particular emphasis on the demonstration of these effects on the quantum dot-photonic crystal platform. Finally, we will focus on the applications of such cavity QED effects.
Nonprobabilistic teleportation of field state via cavity QED
De Carvalho, C R; Jalbert, G; Garreau, J C; Carvalho, Carlos Renato De; Guerra, Emerson S.; Jalbert, Ginette; Garreau, Jean Claude
2007-01-01
In this article we discuss a teleportation scheme of coherent states of cavity field. The experimental realization proposed makes use of cavity quatum electrodynamics involving the interaction of Rydberg atoms with micromaser and Ramsey cavities. In our scheme the Ramsey cavities and the atoms play the role of auxiliary systems used to teleport the state from a micromaser cavity to another. We show that, even if the correct atomic detection fails in the first trials, one can succeed in teleportating the cavity field state if the proper measurement occurs in a later atom.
Nonprobabilistic teleportation of a field state via cavity QED
Carvalho, C R [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Cx. Postal 68528, 21941-972 Rio de Janeiro, RJ (Brazil); Guerra, E S [Departamento de Fisica, Universidade Federal Rural do Rio de Janeiro, Cx. Postal 23851, 23890-000 Seropedica, RJ (Brazil); Jalbert, Ginette [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Cx. Postal 68528, 21941-972 Rio de Janeiro, RJ (Brazil); Garreau, J C [Laboratoire de Physique des Lasers, Atomes et Molecules, Universite des Sciences et Technologies de Lille, Bat. P5, F-59650 Villeneuve d' Ascq Cedex (France)
2007-03-28
In this paper, we discuss a teleportation scheme of coherent states of a cavity field. The experimental realization proposed makes use of cavity quantum electrodynamics, involving the interaction of Rydberg atoms with micromaser and Ramsey cavities. In our scheme the Ramsey cavities and the atoms play the role of auxiliary systems used to teleport the state from one micromaser cavity to another. We show that, even if the correct atomic detection fails in the first trials, one can succeed in teleportating the cavity field state if proper measurement occurs in a later atom.
Fabrication of Glass Micro-Cavities for Cavity QED Experiments
Roy, Arpan
2011-01-01
We report a process for fabricating high quality, defect-free spherical mirror templates suitable for developing high finesse optical Fabry-Perot resonators. The process utilizes the controlled reflow of borosilicate glass and differential pressure to produce mirrors with 0.3 nanometer surface roughness. The dimensions of the mirrors are in the 0.5-5mm range making them suitable candidates for integration with on-chip neutral atom and ion experiments where enhanced interaction between atoms and photons are required. Moreover the mirror curvature, dimension and placement is readily controlled and the process can easily provide an array of such mirrors. We show that cavities constructed with these mirror templates are well suited to quantum information applications such as single photon sources and atom-photon entanglement.
Dynamical Properties of Two Coupled Dissipative QED Cavities Driven by Coherent Fields
无
2007-01-01
When two identical QED cavities driven by the coherent fields are located in a uniform environment, in addition to dissipation, there appears an indirect coupling between the two cavities induced by the background fields. We investigate the effects of the coherent fields, the dissipation as well as the incoherent coupling on the following dynamical properties of the system: photon transfer, reversible decoherence, and quantum state transfer, etc. We find that the photons in the cavities do not leak completely into the environment due to the collective coupling between the cavities and the enviroment, and the photons are transferred irreversibly from the cavity with more photons to the cavity with less ones due to the incoherent coupling so that they are equally distributed among the two cavities. The coherent field pumping on the two cavities increases the mean photons, complements the revived magnitude of the reversible decoherence, but hinders the quantum state transfer between the two cavities. The above phenomena may find applications in quantum communication and other basic fields.
Scheme for implementing quantum dense coding with W-class state in cavity QED
He Juan; Ye Liu; Ni Zhi-Xiang
2008-01-01
An experimentally feasible protocol for realizing dense coding by using a class of W-state in cavity quantum electrodynamics (QED) is proposed in this paper.The prominent advantage of our scheme is that the succeasful probability of the dense coding with a W-class state can reach 1.In addition,the scheme can be implemented by the present cavity QED techniques.
Scheme to Implement Scheme 1 → M Economical Phase-Covariant Telecloning via Cavity QED
LIU Qi; ZHANG Wen-Hai; YE Liu
2008-01-01
We propose an experimentally feasible scheme to implement the economical 1 → M(M = 2k + 1) phase-covariant telecloning without ancilla based on cavity QED. The scheme requires cavity-assisted collision processes between atoms, which cross through the off-resonant cavity field in the vacuum states. During the telecloning process, the cavity is only virtually excited and it thus greatly prolongs the efficient decoherent time. Therefore, our scheme may be realized in experiment in future.
Local and non-local Schroedinger cat states in cavity QED
Full text: I will review recent experiments performed on mesoscopic state superpositions of field states in cavity QED. Proposals to extend these studies to Schroedinger cat states delocalized in two cavities will be discussed. New versions of Bell's inequality tests will probe the non-local behavior of these cats and study their sensitivity to decoherence. (author)
A scheme for implementing quantum clock synchronization algorithm in cavity QED
Wu Qin-Qin; Kuang Le-Man
2006-01-01
In this paper, we propose a scheme for implementing the quantum clock synchronization (QCS) algorithm in cavity quantum electrodynamic (QED) formalism. Our method is based on three-level ladder-type atoms interacting with classical and quantized cavity fields. Atom-qubit realizations of three-qubit and four-qubit QCS algorithms are explicitly presented.
Extended Jaynes-Cummings Models In Cavity Qed
Larson, Jonas
2005-01-01
Due to the improvement within cavity quantum electrodynamics experiments during the last decades, what was former seen as 'toy models' are today realized in laboratories. A controlled isolated coherent evolution of one or a few atoms coupled to a single mode inside a cavity is achievable. Such systems are well suited for studying purely quantum mechanical effects, and also for performing quantum gates, necessary for quantum computing. The Jaynes-Cummings model has served as a theoretical desc...
Quantum optics and cavity QED with quantum dots in photonic crystals
Vuckovic, Jelena
2014-01-01
This chapter will primarily focus on the studies of quantum optics with semiconductor, epitaxially grown quantum dots embedded in photonic crystal cavities. We will start by giving brief introductions into photonic crystals and quantum dots, then proceed with the introduction to cavity quantum electrodynamics (QED) effects, with a particular emphasis on the demonstration of these effects on the quantum dot-photonic crystal platform. Finally, we will focus on the applications of such cavity QE...
Teleportation of GHZ-States in QED-Cavities without the Explicit Bell-State Measurement
Cardoso, W. B.
2008-04-01
In this paper we show how to teleport N-entangled states of N-QED-cavities without Bell-state measurements. The method has potential application in teleportation schemes requiring multipartite entanglements. The success probability and fidelity of the teleportation are also considered.
Scheme for Implementing Teleporting an Arbitrary Tripartite Entangled State in Cavity QED
Wang, Xue-Wen; Peng, Zhao-Hui
2009-10-01
We propose to teleport an arbitrary tripartite entangled state in cavity QED. In this scheme, the five-qubit Brown state is chosen as the quantum channel. It has been shown that the teleportation protocol can be completed perfectly with two different measurement methods. In the future, our scheme might be realizable based on present experimental technology.
Geometric phase in cavity QED containing a nonlinear optical medium and a quantum well
Mohamed, A.-B. A.; Eleuch, H.
2015-11-01
The geometric phase (GP) in cavity QED filled with a nonlinear medium and containing a quantum well is analyzed. We observe collapses and revivals. The optical nonlinearity leads to high frequency oscillations of the GP. The GP is very sensitive not only to the dissipation rates but also to the amplitude of the laser pump.
Bloch-wave engineered submicron-diameter quantum-dot micropillars for cavity QED experiments
Gregersen, Niels; Lermer, Matthias; Reitzenstein, Stephan;
2013-01-01
The semiconductor micropillar is attractive for cavity QED experiments. For strong coupling, the figure of merit is proportional to Q/√V, and a design combining a high Q and a low mode volume V is thus desired. However, for the standard submicron diameter design, poor mode matching between the...
Bloch-wave engineered submicron-diameter quantum-dot micropillars for cavity QED experiments
Gregersen, Niels; Lermer, Matthias; Reitzenstein, Stephan;
2013-01-01
The semiconductor micropillar is attractive for cavity QED experiments. For strong coupling, the figure of merit is proportional to Q/√V, and a design combining a high Q and a low mode volume V is thus desired. However, for the standard submicron diameter design, poor mode matching between the ca...
Probabilistic cloning of a single-atom state via cavity QED
Zhang, Wen; Rui, Pinshu; Lu, Yan; Yang, Qun; Zhao, Yan
2015-06-01
We propose a scheme for probabilistically cloning a two-level state of an atom to a polarization photon via cavity QED system combined with linear optics elements. By choosing appropriate parameters, a controlled phase flip (CPF) gate between the atom and the probe photon is realized. Then we can judge that the cloning process should be continued (with the optimal probability) or interrupted by detecting the probe photon. If the cloning can be continued, the original atom state is deterministically cloned to the cloning photon by performing two more CPF gates and three single-qubit unitary operations. Otherwise, if the detection shows that the cloning should be interrupted, the cloning photon and the relevant operations are omitted.
Zhang, Shu-Qun; Chen, Zhi-De
2014-02-01
We present nonperturbative treatment of the vacuum field bath for two cases, a two-level emitter (TLE) in free space and a lossy TLE coupled to a cavity mode (CM), and the condition that guarantees the validity of the perturbative treatment in both cases is studied. It is shown that the perturbative treatment in the first case is always valid for a real system. In the second case, nevertheless, the perturbative treatment ignores a coupling term, which can bring effects similar to a phonon bath, e.g., coupling renormalization, off-resonance assisted feeding, and pure dephasing inside the resonance region. All of these effects are important for understanding the experimental observations, including the far-off-resonance cavity fluorescence and the additional CM line inside the resonance region in the strong coupling regime.
Multipartite entangled states in coupled quantum dots and cavity QED
We investigate the generation of multipartite entangled state in a system of N quantum dots embedded in a microcavity and examine the emergence of genuine multipartite entanglement by three different characterizations of entanglement. At certain times of dynamical evolution one can generate multipartite entangled coherent exciton states or multiqubit W states by initially preparing the cavity field in a superposition of coherent states or the Fock state with one photon, respectively. Finally, we study environmental effects on multipartite entanglement generation and find that the decay rate for the entanglement is proportional to the number of excitons
Preparation of the W state via cavity QED
ZHANG Jin; YE Liu
2004-01-01
A scheme for preparation of the tripartite W state via cavity quantum electrodynamics is presented in this paper. And the scheme can be generalized to prepare the n-atom W states. The second part of this paper shows how to prepare n-cavity W states. All cavities involved are initially in the vacuum states, thus the requirement on the quality factor of the cavities is greatly loosened.
A simple scheme for generating multi-atom GHZ state via cavity QED
Wang Jun; Yu Long-Bao; Ye Liu
2007-01-01
This paper proposes a simple scheme for generating a three-atom GHZ state via cavity quantum electrodynamics (QED). The task can be achieved through the interaction between two EPR states, which can be prepared easily with current technology. In this scheme, the cavity field is only virtually excited during the interaction process, and no quantum information transfer between the atoms and the cavity is required. Thus it greatly prolongs the efficient decoherent time. Moreover, this scheme is also applicable for generating an .N-atom GHZ state.
Teleportation of a two-atom entangled state using a single EPR pair in cavity QED
Ji Xin; Li Ke; Zhang Shou
2006-01-01
We propose a scheme for teleporting a two-atom entangled state in cavity quantum electrodynamics(QED).In the scheme,we choose a single Einstein-Podolsky-Rosen (EPR) pair as the quantum channel which is shared by the sender and the receiver.By using the atom-cavity-field interaction and introducing an additional atom,we can teleport the two-atom entangled state successfully with a probability of 1.0.Moreover,we show that the scheme is insensitive to cavity decay and thermal field.
Unified single-photon and single-electron counting statistics: From cavity QED to electron transport
A key ingredient of cavity QED is the coupling between the discrete energy levels of an atom and photons in a single-mode cavity. The addition of periodic ultrashort laser pulses allows one to use such a system as a source of single photons--a vital ingredient in quantum information and optical computing schemes. Here we analyze and time-adjust the photon-counting statistics of such a single-photon source and show that the photon statistics can be described by a simple transport-like nonequilibrium model. We then show that there is a one-to-one correspondence of this model to that of nonequilibrium transport of electrons through a double quantum dot nanostructure, unifying the fields of photon-counting statistics and electron-transport statistics. This correspondence empowers us to adapt several tools previously used for detecting quantum behavior in electron-transport systems (e.g., super-Poissonian shot noise and an extension of the Leggett-Garg inequality) to single-photon-source experiments.
Manipulating nanoscale atom-atom interactions with cavity QED
Pal, Arpita; Deb, Bimalendu
2016-01-01
We theoretically explore manipulation of interactions between excited and ground state atoms at nanoscale separations by cavity quantum electrodynamics (CQED). We develop an adiabatic molecular dressed state formalism and show that it is possible to generate Fano-Feshbach resonances between ground and long-lived excited-state atoms inside a cavity. The resonances are shown to arise due to non-adiabatic coupling near a pseudo-crossing between the dressed state potentials. We illustrate our results with a model study using fermionic $^{171}$Yb atoms in a two-modal cavity. Our study is important for manipulation of interatomic interactions at low energy by cavity field.
Photon Berry phases, Instantons and Schrodinger Cats with oscillating parities in cavity QED
Yi-Xiang, Yu; Liu, W M; Zhang, CunLin
2015-01-01
The four standard quantum optics model in cavity QED such as Rabi, Dicke, Jaynes-Cummings ( JC ) and Tavis-Cummings (TC) model were proposed many decades ago. Despite their relative simple forms and many previous theoretical works, their solutions at a finite $ N $ inside the superradiant regime remain unknown. In view of recent remarkable experimental advances in several experimental systems such as cold atoms inside a cavity or superconducting qubits inside a microcavity to realize these models, it becomes topical and important to understand what would be the new phenomena in these models at a finite $ N $, especially inside the superradaint regime. In this work, we resolved this outstanding problem. We use three independent methods such as $ 1/J $ expansion, the strong coupling expansion and exact diagonization (ED) to study $ U(1)/Z_2 $ Dicke model at a finite $ N $ and different anisotropy parameters $ 0 \\leq \\beta \\leq 1 $ as the atom-photon interaction strength increases. This model include the four st...
Novel High Cooperativity Photon-Magnon Cavity QED
Tobar, Michael; Bourhill, Jeremy; Kostylev, Nikita; G, Maxim; Creedon, Daniel
Novel microwave cavities are presented, which couple photons and magnons in YIG spheres in a super- and ultra-strong way at around 20 mK in temperature. Few/Single photon couplings (or normal mode splitting, 2g) of more than 6 GHz at microwave frequencies are obtained. Types of cavities include multiple post reentrant cavities, which co-couple photons at different frequencies with a coupling greater that the free spectral range, as well as spherical loaded dielectric cavity resonators. In such cavities we show that the bare dielectric properties can be obtained by polarizing all magnon modes to high energy using a 7 Tesla magnet. We also show that at zero-field, collective effects of the spins significantly perturb the photon modes. Other effects like time-reversal symmetry breaking are observed.
Perturbative approach to open circuit QED systems
Li, Andy C. Y.; Petruccione, Francesco; Koch, Jens
2014-03-01
Perturbation theory (PT) is a powerful and commonly used tool in the investigation of closed quantum systems. In the context of open quantum systems, PT based on the Markovian quantum master equation is much less developed. The investigation of open systems mostly relies on exact diagonalization of the Liouville superoperator or quantum trajectories. In this approach, the system size is rather limited by current computational capabilities. Analogous to closed-system PT, we develop a PT suitable for open quantum systems. The proposed method is useful in the analytical understanding of open systems as well as in the numerical calculation of system observables, which would otherwise be impractical. This enables us to investigate a variety of open circuit QED systems, including the open Jaynes-Cummings lattice model.
Probabilistic Teleportation of an Arbitrary Two-Atom State in Cavity QED
We propose a scheme for the teleportation of an arbitrary two-atom state by using two pairs of two-atom nonmaximally entangled states as the quantum channel in cavity QED. It is shown that no matter whether the arbitrary two-atom pure state to be teleported is entangled or not, our teleportation scheme can always be probabilistically realized. The success probability of teleportation is determined by the smaller coefficients of the two initially entangled atom pairs.
Probabilistic Teleportation of an Arbitrary Two-Atom State in Cavity QED
LIU Jin-Ming
2007-01-01
We propose a scheme for the teleportation of an arbitrary two-atom state by using two pairs of two-atom nonmaximally entangled states as the quantum channel in cavity QED.It is shown that no matter whether the arbitrary two-atom pure state to be teleported is entangled or not,our teleportation scheme can always be probabilistically realized.The success probability of teleportation is determined by the smaller coefficients of the two initially entangled atom pairs.
Scheme for realizing assisted cloning of an unknown two-atom entangled state via cavity QED
Zhan You-Bang
2008-01-01
This paper proposes a scheme where one can realize quantum cloning of an unknown two-atom entangled state with assistance of a state preparer in cavity QED.The first stage of the scheme requires usual teleportation.In the second stage of the scheme,with the assistance of the preparer,the perfect copies of an unknown atomic entangled state can be produced.
Realization of atomic GHZ states via cavity QED
In this work we propose a scheme in which it is possible to generate atomic GHZ states by letting three-level atoms in a lambda configuration to interact with a cavity field followed by a displacement of the cavity field and a selective measurements on two-level atoms which disentangle the atoms and field states. We also propose a GHZ test based on such states. (author)
High flux cold Rubidium atomic beam for strongly coupled Cavity QED
Roy, Basudev
2012-01-01
This paper presents a setup capable of producing a high-flux continuous beam of cold rubidium atoms for cavity QED experiments in the regime of strong coupling. A 2 $D^+$ MOT, loaded by rubidium getters in a dry film coated vapor cell, fed a secondary moving-molasses MOT (MM-MOT) at a rate of 1.5 x $10^{10}$ atoms/sec. The MM-MOT provided a continuous beam with tunable velocity. This beam was then directed through the waist of a 280 $\\mu$m cavity resulting in a Rabi splitting of more than +/- 10 MHz. The presence of sufficient number of atoms in the cavity mode also enabled splitting in the polarization perpendicular to the input. The cavity was in the strong coupling regime, with parameters (g, $\\kappa$, $\\gamma$)/2$\\pi$ equal to (7, 3, 6)/ 2$\\pi$ MHz.
Teleportation of atomic and photonic states in low-Q cavity QED
Peng, Zhao-Hui; Zou, Jian; Liu, Xiao-Juan; Kuang, Le-Man
2012-11-01
We propose two alternative teleportation protocols in low-Q cavity QED. Through the input-output process of photons, we can generate atom-photon entangled states as the quantum channel. Then we propose to teleport single-atom (two-atom entangled) state using coherent photonic states, and to teleport single photonic state with the assistance of three-level atom. The distinct feature of our protocols is that we can teleport both atomic and photonic states via the input-output process of photons in the low-Q cavity. Furthermore, as our protocols work in low-Q cavities and only involve virtual excitation of atoms, they are insensitive to both cavity decay and atomic spontaneous emission, and may be feasible with current technology.
Alternative Scheme for Teleportation of Two-Atom Entangled State in Cavity QED
YANG Zhen-Biao
2006-01-01
We have proposed an alternative scheme for teleportation of two-atom entangled state in cavity QED. It is based on the degenerate Raman interaction of a single-mode cavity field with a ∧-type three-level atom. The prominent feature of the scheme is that only one cavity is required, which is prior to the previous one. Moreover, the atoms need to be detected are reduced compared with the previous scheme. The experimental feasibility of the scheme is discussed.The scheme can easily be generalized for teleportation of N-atom GHZ entangled states. The number of the atoms needed to be detected does not increase as the number of the atoms in GHZ state increases.
Implementation of a many-qubit Grover search by cavity QED
Fan Hao-Quan; Yang Wan-Li; Huang Xue-Ren; Feng Mang
2009-01-01
We explore the possibility of an N-qubit (N>3) Grover search in cavity QED, based on a fast operation of an N-qubit controlled phase-flip with atoms in resonance with the cavity mode. We demonstrate both analytically and numerically that our scheme can be achieved efficiently to find a marked state with high fidelity and high success probability. As an example, a ten-qubit Grover search is simulated specifically under the discussion of experimental feasibility and challenge. We argue that our scheme is applicable to the case involving an arbitrary number of qubits. As cavity decay is involved in our quantum trajectory treatment, we can analytically understand the implementation of a Grover search subject to dissipation, which will be very helpful for relevant experiments.
From blockade to transparency: controllable photon transmission through a circuit QED system
Liu, Yu-xi; Xu, Xun-Wei; Miranowicz, Adam; Nori, Franco
2012-01-01
A strong photon-photon nonlinear interaction is a necessary condition for photon blockade. Moreover, this nonlinearity can also result a bistable behavior in the cavity field. We analyze the relation between detecting field and photon blockade in a superconducting circuit QED system, and show that photon blockade cannot occur when the detecting field is in the bistable regime. This photon blockade is the microwave-photonics analog of the Coulomb blockade. We further demonstrate that the photo...
Strategies for real-time position control of a single atom in cavity QED
Recent realizations of single-atom trapping and tracking in cavity QED open the door for feedback schemes which actively stabilize the motion of a single atom in real time. We present feedback algorithms for cooling the radial component of motion for a single atom trapped by strong coupling to single-photon fields in an optical cavity. Performance of various algorithms is studied through simulations of single-atom trajectories, with full dynamical and measurement noise included. Closed loop feedback algorithms compare favourably to open loop 'switching' analogues, demonstrating the importance of applying actual position information in real time. The high optical information rate in current experiments enables real-time tracking that approaches the standard quantum limit for broadband position measurements, suggesting that realistic active feedback schemes may reach a regime where measurement backaction appreciably alters the motional dynamics
Realization of a bipolar atomic Solc filter in the cavity-QED microlaser
We report experimental realization of a rudimentary atomic Solc filter, recently proposed by Hong et al. [Opt. Express 17, 15455 (2009)]. It is realized by employing a bipolar atom-cavity coupling constant in the cavity-QED microlaser operating with a TEM10 mode in a strong coupling regime. The polarity flip in the coupling constant dramatically changes the photoemission probability of a two-level atom relative to unipolar coupling, resulting in multiple narrow emission bands in the detuning curve of the microlaser mean photon number. The observed resonance curves are explained well by a two-step, three-dimensional, geodesic-like motion of the Bloch vector in the semiclassical limit.
Two-Frequency Jahn-Teller Systems in Circuit QED
Dereli, Tekin; Müstecaplıoğlu, Özgür E
2011-01-01
We investigate simulating two-frequency (two-mode) jahn-Teller systems in Circuit QED. Our system is composed of two superconducting transmission line resonators interacting with a common flux qubit in the ultrastrong coupling regime. We translate the quantum optical Circuit QED model of the system to an extended two-mode Jahn-Teller Hamiltonian. It is shown that the system can be tuned to an effective single mode Hamiltonian systematically from the two-mode model the varying the coupling strength between the resonators.
Role of the lightmatter coupling strength on nonMarkovian phonon effects in semiconductor cavity QED
Nielsen, Per Kær; Nielsen, Torben Roland; Lodahl, Peter;
2011-01-01
Semiconductor cavity quantum electrodynamical (CQED) devices are believed to be important components for future quantum information technologies. Being composed of a single quantum dot (QD) embedded in a cavity, semiconductor CQED systems resemble atomic CQED systems. However, recent experiments [1...
Transferring of a Two-Mode Entangled State Between Two Cavities via Cavity QED
WU Tao; NI Zhi-Xiang; YE Liu
2007-01-01
We propose a scheme for transferring of a two-mode entanglement of zero- or one-photon entangled states between two cavities via atom-cavity field resonant interaction.In our proposal,in order to transfer the entangled state,we only need two identical two-level atoms and a two-mode cavity for receiving the teleported state.This scheme does not require Bell-state measurement and performing any transformations to reconstruct the initial state.And the transfer can occur with 100% success probability in a simple manner.And a network for transferring of a two-mode entangled state between cavities is suggested.This scheme can also be extended to transfer N-mode entangled state of cavity.
无
2009-01-01
A scheme is proposed to simulate the Ising model and preserve the maximum entangled states (Bell states) in cavity quantum electrodynamics (QED) driven by a classical field with large detuning. In the strong driving and large-detuning regime, the effective Hamiltonian of the system is the same as the standard Ising model, and the scheme can also make the initial four Bell states of two atoms at the maximum entanglement all the time. So it is a simple memory for the maximal entangled states. The system is insensitive to the cavity decay and the thermal field and more immune to decoherence. These advantages can warrant the experimental feasibility of the current scheme. Furthermore, the genuine four-atom entanglement may be acquired via two Bell states through one-step implementation on four two-level atoms in the strong-driven model, and when two Greenberger-Horne-Zeilinger (GHZ) states are prepared in our scheme, the entangled cluster state may be acquired easily. The success probability for the scheme is 1.
A scheme is proposed for the controlled teleportation of an arbitrary two-atom state via special W-type entangled states and QED cavity. The scheme does not involve the direct joint Bell-state-measurement (BSM). We show that the quantum information is split into two parts, thus the original atomic state cannot be perfectly restored by the receiver without the other agent's collaboration and classical communication. In addition, the physical realization of this scheme is not difficult
Generation of Maximally Entangled States of Two Nonidentical Atoms in Cavity QED
LIYu-Liang; ZHOUZheng-Wei; PANGChao-Yang; GUOGuang-Can
2005-01-01
We have discussed the system which consists of two nonidentical two-level atoms trapped simultaneously in a large-detuned single-mode cavity field in this paper. The results show that it is possible to generate maximally entangled states for two nonidentical two-level atoms only if the cavity frequency and difference of two nonidentical atoms transition frequency are selected and the cavity-atom interacation time is controlled.
Photon collection from a trapped ion--cavity system
Sterk, J. D.; Luo, L.; Manning, T. A.; P. Maunz; Monroe, C.
2011-01-01
We present the design and implementation of a trapped ion cavity QED system. A single ytterbium ion is confined by a micron-scale ion trap inside a 2 mm optical cavity. The ion is coherently pumped by near resonant laser light while the cavity output is monitored as a function of pump intensity and cavity detuning. We observe a Purcell enhancement of scattered light into the solid angle subtended by the optical cavity, as well as a three-peak structure arising from strongly driving the atom. ...
Fusion of entangled coherent W and GHZ states in cavity QED
Zang, Xue-Ping; Yang, Ming; Song, Wei; Cao, Zhuo-Liang
2016-07-01
Efficient preparation of W and GHZ states encoded in various degrees of freedom of quantum particles is vital in quantum information science. So far, most of the studies have focused on polarization encoded photonic W and GHZ states. In this paper, we focus on W- and GHZ-class entangled coherent states, and propose schemes to fuse small W- and GHZ-entangled coherent states into larger ones. Based on successive detuned interactions between optical modes and an ancilla atom, an (N + M - 2)-mode entangled coherent W state can be probabilistically prepared from an N-mode and an M-mode entangled coherent W states. This fusion scheme applies to entangled coherent GHZ states too, and it can succeed in a deterministic way. The ancilla atom only interacts with a single optical mode, which avoids the problem of synchronizing many atoms in the previous cavity QED based fusion schemes. The detuning property of the interaction makes the current fusion scheme more feasible that the ones based on resonant atom-light interactions. In addition, the two levels of the ancilla atom for encoding quantum information are two degenerate ground states, and the excited state is adiabatically eliminated during the fusion process, so the atomic decay from excited states does not affect the quality of the fusion process.
BRAVO for many-server QED systems with finite buffers
Daley, DJ; Leeuwaarden, van, JSH Johan; Nazarathy, Y Yoni
2015-01-01
This paper demonstrates the occurrence of the feature called BRAVO (balancing reduces asymptotic variance of output) for the departure process of a finite-buffer Markovian many-server system in the QED (quality and efficiency-driven) heavy-traffic regime. The results are based on evaluating the limit of an equation for the asymptotic variance of death counts in finite birth-death processes.
Enhancements to cavity quantum electrodynamics system
Cimmarusti, A D; Norris, D G; Orozco, L A
2011-01-01
We show the planned upgrade of a cavity QED experimental apparatus. The system consists of an optical cavity and an ensemble of ultracold $^{85}$Rb atoms coupled to its mode. We propose enhancements to both. First, we document the building process for a new cavity, with a planned finesse of $\\sim$20000. We address problems of maintaining mirror integrity during mounting and improving vibration isolation. Second, we propose improvements to the cold atom source in order to achieve better optical pumping and control over the flux of atoms. We consider a 2-D optical molasses for atomic beam deflection, and show computer simulation results for evaluating the design. We also examine the possibility of all-optical atomic beam focusing, but find that it requires unreasonable experimental parameters.
Two-frequency Jahn-Teller systems in circuit QED
Dereli, Tekin; Gül, Yusuf; Müstecaplıoğlu, Özgür E.; Forn-Diaz, Pol
2012-01-01
PHYSICAL REVIEW A 85, 053841 (2012) Two-frequency Jahn-Teller systems in circuit QED Tekin Dereli,1 Yusuf Gu¨l,1 Pol Forn-D´ıaz,2 and O¨ zgu¨r E. Mu¨stecaplıog˘lu1,* 1Department of Physics, Koc¸ University, Sarıyer, Istanbul, 34450, Turkey 2Norman Bridge Laboratory of Physics, California Institute of Technology, Pasadena, CA 91125, USA (Received 6 September 2011; published 30 May 2012) We investigate the simulation of Jahn-Teller models with two nondegenerate vibrational mod...
QED of lossy cavities: Operator and quantum-state input-output relations
Within the framework of exact quantization of the electromagnetic field in dispersing and absorbing media the input-output problem of a high-Q cavity is studied, with special emphasis on the absorption losses in the coupling mirror. As expected, the cavity modes are found to obey quantum Langevin equations, which could be also obtained from quantum noise theories, by appropriately coupling the cavity modes to dissipative systems, including the effect of the mirror-assisted absorption losses. On the contrary, the operator input-output relations obtained in this way would be incomplete in general, as the exact calculation shows. On the basis of the operator input-output relations the problem of extracting the quantum state of an initially excited cavity mode is studied and input-output relations for the s-parametrized phase-space function are derived, with special emphasis on the relation between the Wigner functions of the quantum states of the outgoing field and the cavity field
Broadband Waveguide QED System on a Chip
Quan, Qimin; Bulu, Irfan; Loncar, Marko
2009-01-01
We demonstrate that a slot waveguide provides a broadband loss-free platform suitable for applications in quantum optics. We find that strong coupling between light quanta and a single quantum emitter placed in the waveguide slot can be achieved with efficiency higher than 96% and Purcell factor (spontaneous emission factor) larger than 200. The proposed system is a promising platform for quantum information processing and can be used to realize an efficient single photon source and optically...
Generation of multipartite entangled states for chains of atoms in the framework of cavity-QED
Cavity quantum electrodynamics is a research field that studies electromagnetic fields in confined spaces and the radiative properties of atoms in such fields. Experimentally, the simplest example of such system is a single atom interacting with modes of a high-finesse resonator. Theoretically, such system bears an excellent framework for quantum information processing in which atoms and light are interpreted as bits of quantum information and their mutual interaction provides a controllable entanglement mechanism. In this thesis, we present several practical schemes for generation of multipartite entangled states for chains of atoms which pass through one or more high-finesse resonators. In the first step, we propose two schemes for generation of one- and two-dimensional cluster states of arbitrary size. These schemes are based on the resonant interaction of a chain of Rydberg atoms with one or more microwave cavities. In the second step, we propose a scheme for generation of multipartite W states. This scheme is based on the off-resonant interaction of a chain of three-level atoms with an optical cavity and a laser beam. We describe in details all the individual steps which are required to realize the proposed schemes and, moreover, we discuss several techniques to reveal the non-classical correlations associated with generated small-sized entangled states. (orig.)
Generation of multipartite entangled states for chains of atoms in the framework of cavity-QED
Gonta, Denis
2010-07-07
Cavity quantum electrodynamics is a research field that studies electromagnetic fields in confined spaces and the radiative properties of atoms in such fields. Experimentally, the simplest example of such system is a single atom interacting with modes of a high-finesse resonator. Theoretically, such system bears an excellent framework for quantum information processing in which atoms and light are interpreted as bits of quantum information and their mutual interaction provides a controllable entanglement mechanism. In this thesis, we present several practical schemes for generation of multipartite entangled states for chains of atoms which pass through one or more high-finesse resonators. In the first step, we propose two schemes for generation of one- and two-dimensional cluster states of arbitrary size. These schemes are based on the resonant interaction of a chain of Rydberg atoms with one or more microwave cavities. In the second step, we propose a scheme for generation of multipartite W states. This scheme is based on the off-resonant interaction of a chain of three-level atoms with an optical cavity and a laser beam. We describe in details all the individual steps which are required to realize the proposed schemes and, moreover, we discuss several techniques to reveal the non-classical correlations associated with generated small-sized entangled states. (orig.)
On superradiant phase transitions and effective models in circuit QED
Circuit QED systems of artificial atoms interacting with microwaves have been proved to behave in many respects analogously to their counterparts with real atoms in cavity QED. However, it has been predicted recently that the analogy fails if a large number of (artificial) atoms couple strongly to the electromagnetic radiation: Whereas for real atoms a no-go theorem rules out the possibility of a superradiant quantum phase transition as the coupling is increased, the standard description of circuit QED systems by an effective model based on macroscopic quantities does allow it. We investigate the possibility of a superradiant quantum phase transition in circuit QED systems from a microscopic point of view. Our analysis shows that also circuit QED systems are subject to the no-go theorem. It hence restores the analogy of circuit QED and cavity QED and challenges the applicability of the standard description of circuit QED systems in the regime under concern. In the light of this analysis, the no-go theorem is scrutinized and confirmed in a way more adequate for realistic physical systems.
Enhancing Quantum Discord in Cavity QED by Applying Classical Driving Field
QIAN Yi; XU Jing-Bo
2012-01-01
We investigate the quantum discord dynamics in a cavity quantum electrodynamics system, which consists of two noninteracting two-level atoms driven by independent optical Gelds and classical fields, and find that the quantum discord vanishes only asymptotically although entanglement disappears suddenly during the time evolution in the absence of classical fields. It is shown that the amount of quantum discord can be increased by adjusting the classical driving fields because the increasing degree of the amount of quantum mutual information is greater than classical correlation by applying the classical driving fields. Finally, the influence of the classical driving field on the fidelity of the system is also examined.%We investigate the quantum discord dynamics in a cavity quantum electrodynamics system,which consists of two noninteracting two-level atoms driven by independent optical fields and classical fields,and find that the quantum discord vanishes only asymptotically although entanglement disappears suddenly during the time evolution in the absence of classical fields.It is shown that the amount of quantum discord can be increased by adjusting the classical driving fields because the increasing degree of the amount of quantum mutual information is greater than classical correlation by applying the classical driving fields.Finally,the influence of the classical driving field on the fidelity of the system is also examined.
Quantum Dot Cavity-QED in the Presence of Strong Electron-Phonon Interactions
Wilson-Rae, I
2001-01-01
A quantum dot strongly coupled to a single high finesse optical microcavity mode constitutes a new fundamental system for quantum optics. Here, the effect of exciton-phonon interactions on reversible quantum-dot cavity coupling is analysed without making Born-Markov approximation. The analysis is based on techniques that have been used to study the ``spin boson'' Hamiltonian. Observability of vacuum-Rabi splitting depends on the strength and the frequency dependence of the spectral density function characterizing the interactions with phonons, both of which can be influenced by phonon confinement.
Photon-photon interaction in strong-coupling cavity-atom system
Yang, Jian; Kwiat, Paul G. [Department of Physics, University of Illinois at Urbana-Champaign (United States)
2014-12-04
We study photon-photon interactions mediated by a cavity-atom system in the strongcoupling regime of cavity quantum electrodynamics (QED). Different temporal shapes of the incident photons have been explored via numerical calculations. Especially, time-reversed photons can be in the cavity simultaneously and potentially acquire strong interaction with each other, advancing quantum information applications, e.g., quantum non-demolition (QND) measurement.
High-Q submicron-diameter quantum-dot microcavity pillars for cavity QED experiments
Gregersen, Niels; Lermer, Matthias; Dunzer, Florian;
As/AlAs micropillar design where Bloch-wave engineering is employed to significally enhance the cavity mode confinement in the submicron diameter regime. We demonstrate a record-high vacuum Rabi splitting of 85 µeV of the strong coupling for pillars incorporating quantum dots with modest oscillator strength f ≈ 10....... It is well-known that light-matter interaction depends on the photonic environment, and thus proper engineering of the optical mode in microcavity systems is central to obtaining the desired functionality. In the strong coupling regime, the visibility of the Rabi splitting is described by the light...... coupling in micropillars relied on quantum dots with high oscillator strengths f > 50, our advanced design allows for the observation of strong coupling for submicron diameter quantum dot-pillars with standard f ≈ 10 oscillator strength. A quality factor of 13600 and a vacuum Rabi splitting of 85 µeV are...
Meissner-like effect for synthetic gauge field in multimode cavity QED
Ballantine, Kyle E; Keeling, Jonathan
2016-01-01
Previous realizations of synthetic gauge fields for ultracold atoms do not allow the spatial profile of the field to evolve freely. We propose a scheme which overcomes this restriction by using the light in a multimode cavity, in conjunction with Raman coupling, to realize an artificial magnetic field which acts on a Bose-Einstein condensate of neutral atoms. We describe the evolution of such a system, and present the results of numerical simulations which show dynamical coupling between the effective field and the matter on which it acts. Crucially, the freedom of the spatial profile of the field is sufficient to realize a close analogue of the Meissner effect, where the magnetic field is expelled from the superfluid. This back-action of the atoms on the synthetic field distinguishes the Meissner-like effect described here from the Hess-Fairbank suppression of rotation in a neutral superfluid observed elsewhere.
Atoms and Molecules in Cavities: From Weak to Strong Coupling in QED Chemistry
Flick, Johannes; Appel, Heiko; Rubio, Angel
2016-01-01
In this work, we provide an overview of how well-established concepts in the fields of quantum chemistry and material sciences have to be adapted when the quantum nature of light becomes important in correlated matter-photon problems. Therefore, we analyze model systems in optical cavities, where the matter-photon interaction is considered from the weak- to the strong coupling limit and for individual photon modes as well as for the multi-mode case. We identify fundamental changes in Born-Oppenheimer surfaces, spectroscopic quantities, conical intersections and efficiency for quantum control. We conclude by applying our novel recently developed quantum-electrodynamical density-functional theory to single-photon emission and show how a straightforward approximation accurately describes the correlated electron-photon dynamics. This paves the road to describe matter-photon interactions from first-principles and addresses the emergence of new states of matter in chemistry and material science.
Guerra, E S
2004-01-01
In this article we discuss two schemes of teleportation of atomic states. In the first scheme we consider atoms in a three-level cascade configuration and in the second scheme we consider atoms in a three-level lambda configuration. The experimental realization proposed makes use of cavity Quatum Electrodynamics involving the interaction of Rydberg atoms with a micromaser cavity prepared in a state $|\\psi >_{C}=(|0> +|1>)/\\sqrt{2}$
Wu Xi; Chen Zhi-Hua; Zhang Yong; Chen Yue-Hua; Ye Ming-Yong; Lin Xiu-Min
2011-01-01
Schemes are presented for realizing quantum controlled phase gate and preparing an N-qubit W-like state, which are based on the large-detuned interaction among three-state atoms, dual-mode cavity and a classical pulse. In particular, a class of W states that can be used for perfect teleportation and superdense coding is generated by only one step.Compared with the previous schemes, cavity decay is largely suppressed because the cavity is only virtually excited and always in the vacuum state and the atomic spontaneous emission is strongly restrained due to a large atom-field detuning.
Implementation of n-qubit Deutsch-Jozsa algorithm using resonant interaction in cavity QED
Wang Hong-Fu; Zhang Shou
2008-01-01
We propose a scheme to implement the n-qubit Deutsch-Jozsa algorithm based on resonant interaction between the atoms and a single-mode cavity. In the scheme, the resonant transitions between two ground states and one excited state of an atom are changed alternately by adjusting the cavity frequency appropriately, and the operations required to complete the algorithm can be significantly simplified following the increment of the number of qubits. The implementation of the scheme in experiment would show the full power of quantum algorithm and would be significative and important for more complicated quantum algorithm in cavity quantum electrodynamics.
Generation of four-particle GHZ states in bimodal cavity QED
Yang Zhen-Biao
2007-01-01
We propose a scheme for preparing four-particle Greenberger-Horne-Zeilinger states using two identical bimodal cavities, each supports two modes with different frequencies. This scheme is an alternative to another published work[Christopher C Gerry 1996 Phys. Rev. A 53 4591]. Comparisons between them are discussed. The fidelity and the probability of success influenced by cavity decay for the generated states are also considered.
Continuous Pump Assisted Conditional Synthesis of Nonclassical States in a Dispersive Cavity QED
GUOJian-Hong
2003-01-01
The interaction of N identical atoms with both a quantized cavity field and an external classical pumping field with the fields being degenerate in frequency, is studied in the regime where the atoms and fields are highly detuned. This dispersive interaction can be used to generate coherent states for the cavity field. By preparing the injected atoms in a superposition of the bare atomic states, various types of Schroedinger-cat-like states may be generated.
Continuous Pump Assisted Conditional Synthesis of Nonclassical States in a Dispersive Cavity QED
GUO Jian-Hong
2003-01-01
The interaction of N identical atoms with both a quantized cavity field and an external classical pumpingfield with the fields being degenerate in frequency, is studied in the regime where the atoms and fields are highly detuned.This dispersive interaction can be used to generate coherent states for the cavity field. By preparing the injected atomsin a superposition of the bare atomic states, various types of Schrodinger-cat-like states may be generated.
High-flux cold rubidium atomic beam for strongly-coupled cavity QED
This paper presents a setup capable of producing a high-flux continuous beam of cold rubidium atoms for cavity quantum electrodynamics experiments in the region of strong coupling. A 2D+ magneto-optical trap (MOT), loaded with rubidium getters in a dry-film-coated vapor cell, fed a secondary moving-molasses MOT (MM-MOT) at a rate greater than 2 x 1010 atoms/s. The MM-MOT provided a continuous beam with a tunable velocity. This beam was then directed through the waist of a cavity with a length of 280 μm, resulting in a vacuum Rabi splitting of more than ±10 MHz. The presence of a sufficient number of atoms in the cavity mode also enabled splitting in the polarization perpendicular to the input. The cavity was in the strong coupling region, with an atom-photon dipole coupling coefficient g of 7 MHz, a cavity mode decay rate κ of 3 MHz, and a spontaneous emission decay rate γ of 6 MHz.
High-flux cold rubidium atomic beam for strongly-coupled cavity QED
Roy, Basudev [Indian Institute of Science Education and Research, Kolkata (India); University of Maryland, MD (United States); Scholten, Michael [University of Maryland, MD (United States)
2012-08-15
This paper presents a setup capable of producing a high-flux continuous beam of cold rubidium atoms for cavity quantum electrodynamics experiments in the region of strong coupling. A 2D{sup +} magneto-optical trap (MOT), loaded with rubidium getters in a dry-film-coated vapor cell, fed a secondary moving-molasses MOT (MM-MOT) at a rate greater than 2 x 10{sup 10} atoms/s. The MM-MOT provided a continuous beam with a tunable velocity. This beam was then directed through the waist of a cavity with a length of 280 μm, resulting in a vacuum Rabi splitting of more than ±10 MHz. The presence of a sufficient number of atoms in the cavity mode also enabled splitting in the polarization perpendicular to the input. The cavity was in the strong coupling region, with an atom-photon dipole coupling coefficient g of 7 MHz, a cavity mode decay rate κ of 3 MHz, and a spontaneous emission decay rate γ of 6 MHz.
Quantum state engineering and reconstruction in cavity QED. An analytical approach
Lougovski, P.
2004-09-25
The models of a strongly-driven micromaser and a one-atom laser are developed. Their analytical solutions are obtained by means of phase space techniques. It is shown how to exploit the model of a one-atom laser for simultaneous generation and monitoring of the decoherence of the atom-field ''Schroedinger cat'' states. The similar machinery applied to the problem of the generation of the maximally-entangled states of two atoms placed inside an optical cavity permits its analytical solution. The steady-state solution of the problem exhibits a structure in which the two-atom maximally-entangled state correlates with the vacuum state of the cavity. As a consequence, it is demonstrated that the atomic maximally-entangled state, depending on a coupling regime, can be produced via a single or a sequence of no-photon measurements. The question of the implementation of a quantum memory device using a dispersive interaction between the collective internal ground state of an atomic ensemble and two orthogonal modes of a cavity is addressed. The problem of quantum state reconstruction in the context of cavity quantum electrodynamics is considered. The optimal operational definition of the Wigner function of a cavity field is worked out. It is based on the Fresnel transform of the atomic inversion of a probe atom. The general integral transformation for the Wigner function reconstruction of a particle in an arbitrary symmetric potential is derived.
Cavity QED Experiments with Ion Coulomb Crystals. Towards quantum memories and photon counters
Trapped and laser cooled atomic ions in the form of Coulomb crystals represent interesting objects for investigation of Cavity Quantum ElectroDynamics (CQED) and related phenomena. First of all, the number and density of atoms in such crystals as well as the shapes of the crystals can relatively easily be controlled. Second, the ion-ion Coulomb repulsion results in an essentially collision-free environment with the prospect of long coherence times. These properties were recently exploited in experiments focused on investigations of the collective coupling of cold ion ensembles to light modes of a Fabry-Perot cavity, as well as in demonstration of cavity Electromagnetically induced Transparency (EIT) and a photon blockade mechanism. The next step of these experiments will be to realize a light storage scheme, partly for demonstrating an efficient photon counting device and partly for eventually establishing a quantum memory for light with both high efficiency and fidelity. (author)
Nielsen, Per Kær; Nielsen, Torben Roland; Lodahl, P.;
2012-01-01
dependencies are covered. We find that in general the electron-phonon interaction gives rise to a greatly increased bandwidth of the coupling between quantum dot and cavity. At low temperature, an asymmetry in the quantum dot decay rate is observed, leading to a faster decay when the quantum dot has a larger...
Influence of the Stark Shift on Entanglement Sudden Death and Birth in Cavity QED
ZHANG Jian-Song; CHEN Ai-Xi; WU Kun-Hua
2011-01-01
We investigate the entanglement dynamics of two two-level atoms interacting with two vacuum fields of two spatially separated cavities with the Stark effects by employing the concurrence. It is shown that the entanglement sudden death (ESD) and birth (ESB) could be controlled by adjusting the Stark-shift parameters. If the Stark-shift parameters are chosen appropriately, then ESD and ESB phenomena will appear. In addition, the appearance of ESD before or after ESB depends on the Stark-shift values.
Quantum state engineering and reconstruction in cavity QED: An analytical approach
Lougovski, Pavel
2004-01-01
The models of a strongly-driven micromaser and a one-atom laser are developed. Their analytical solutions are obtained by means of phase space techniques. It is shown how to exploit the model of a one-atom laser for simultaneous generation and monitoring of the decoherence of the atom-field "Schrödinger cat" states. The similar machinery applied to the problem of the generation of the maximally-entangled states of two atoms placed inside an optical cavity permits its analytical solution. The ...
GUO Jian-Hong
2004-01-01
The interaction of N two-level atoms with both a two-mode cavity field and an external classical pumping field, and with the fields being degenerate in frequency, is studied in the regime where the atoms and fields are highly detuned. This dispersive interaction can be used to generate a large number of important entangled coherent states conditional on the initial atomic states and state-selective measurements. A dynamical relation is established between the results for the case with continuous pumping and the case without external driving where the coherent field is put in as the initial condition.
Macroscopic Quantum Criticality in a Circuit QED
Wang, Y D; Nori, F; Quan, H T; Sun, C P; Liu, Yu-xi; Nori, Franco
2006-01-01
Cavity quantum electrodynamic (QED) is studied for two strongly-coupled charge qubits interacting with a single-mode quantized field, which is provided by a on-chip transmission line resonator. We analyze the dressed state structure of this superconducting circuit QED system and the selection rules of electromagnetic-induced transitions between any two of these dressed states. Its macroscopic quantum criticality, in the form of ground state level crossing, is also analyzed, resulting from competition between the Ising-type inter-qubit coupling and the controllable on-site potentials.
We propose a way for generating n-qubit Greenberger-Horne-Zeilinger (GHZ) entangled states with a three-level qubit system and (n-1) four-level qubit systems in a cavity. This proposal does not require identical qubit-cavity coupling constants and thus is tolerant to qubit-system parameter nonuniformity and nonexact placement of qubits in a cavity. The proposal does not require adjustment of the qubit-system level spacings during the entire operation. Moreover, it is shown that entanglement can be deterministically generated using this method and the operation time is independent of the number of qubits. The present proposal is quite general, which can be applied to physical systems such as various types of superconducting devices coupled to a resonator or atoms trapped in a cavity.
From strong to ultrastrong coupling in circuit QED architectures
The field of cavity quantum electrodynamics (cavity QED) studies the interaction between light and matter on a fundamental level: a single atom interacts with a single photon. If the atom-photon coupling is larger than any dissipative effects, the system enters the strong-coupling limit. A peculiarity of this regime is the possibility to form coherent superpositions of light and matter excitations - a kind of 'molecule' consisting of an atomic and a photonic contribution. The novel research field of circuit QED extends cavity QED concepts to solid-state based system. Here, a superconducting quantum bit is coupled to an on-chip superconducting one-dimensional waveguide resonator. Owing to the small mode-volume of the resonant cavity, the large dipole moment of the 'artificial atom' and the enormous engineering potential inherent to superconducting quantum circuits, remarkable atom-photon coupling strengths can be realized. This thesis describes the theoretical framework, the development of fabrication techniques and the implementation of experimental characterization techniques for superconducting quantum circuits for circuit QED applications. In particular, we study the interaction between superconducting flux quantum bits and high-quality coplanar waveguide resonators in the strong-coupling limit. Furthermore, we report on the first experimental realization of a circuit QED system operating in the ultrastrong-coupling regime, where the atom-photon coupling rate reaches a considerable fraction of the relevant system frequencies. In these experiments we could observe phenomena that can not be explained within the renowned Jaynes-Cummings model. (orig.)
General QED/QCD aspects of simple systems
This paper discusses the following topics: renormalization theory; the Kinoshita-Lee-Nauenberg theorem; the Yennie-Frautschi-Suura relation; scale invariance at large momentum transfer; scaling and scaling violation at large momentum transfers; low-energy theorem in Compton scattering; does the perturbation series in QED converge; renormalization of the weak angle Θw; the Nambu-Bethe-Salpeter (NBS) equation; the decay rate of 3S, positronium; radiative corrections to QCD Born cross section; and progress on the relativistic 2-body equation
Coto, Raul; Orszag, Miguel
2014-05-01
Multipartite quantum correlation is one of the most relevant indicators of the quantumness of a system in many body systems. This remarkable feature is in general difficult to characterize and the known definitions are hard to measure. Besides the efforts dedicated to solve this problem, the question of which is the best approach remains open. In this paper, we study the global quantum discord (GQD) as a bipartite and multipartite measure. We also check the limits of this definition and present an experimental scheme to determine the maximum of the GQD via the measurements of the system’s excitations, during the time evolution of the present system.
Controlling entanglement sudden death in cavity QED by classical driving fields
Zhang, Jian-Song; Xu, Jing-Bo; Lin, Qiang
2008-01-01
We investigate the entanglement dynamics of a quantum system consisting of two-level atoms interacting with vacuum or thermal fields with classical driving fields. We find that the entanglement of the system can be improved by adjusting the classical driving field. The influence of the classical field and the purity of the initial state on the entanglement sudden death is also studied. It is shown that the time of entanglement sudden death can be controlled by the classical driving fields. Pa...
Quantum optics and cavity QED Quantum network with individual atoms and photons
Rempe G.
2013-08-01
Full Text Available Quantum physics allows a new approach to information processing. A grand challenge is the realization of a quantum network for long-distance quantum communication and large-scale quantum simulation. This paper highlights a first implementation of an elementary quantum network with two fibre-linked high-finesse optical resonators, each containing a single quasi-permanently trapped atom as a stationary quantum node. Reversible quantum state transfer between the two atoms and entanglement of the two atoms are achieved by the controlled exchange of a time-symmetric single photon. This approach to quantum networking is efficient and offers a clear perspective for scalability. It allows for arbitrary topologies and features controlled connectivity as well as, in principle, infinite-range interactions. Our system constitutes the largest man-made material quantum system to date and is an ideal test bed for fundamental investigations, e.g. quantum non-locality.
Pfaffian states in coupled atom-cavity systems
Hayward, Andrew L. C.; Martin, Andrew M.
2016-05-01
Coupled atom-cavity arrays, such as those described by the Jaynes-Cummings-Hubbard model, have the potential to emulate a wide range of condensed-matter phenomena. In particular, the strongly correlated states of the fractional quantum Hall effect can be realized. At some filling fractions, the fraction quantum Hall effect has been shown to possess ground states with non-Abelian excitations. The most well studied of these states is the Pfaffian state of Moore and Read G. Moore and N. Read, Nucl. Phys. B 360, 362 (1991), 10.1016/0550-3213(91)90407-O, which is the ground state of a Hall liquid with a three-body interaction. We show how an effective three-body interaction can be generated within the cavity QED framework, and that a Pfaffian-like ground state of these systems exists.
Photon transport in a one-dimensional nanophotonic waveguide QED system
Liao, Zeyang; Zeng, Xiaodong; Nha, Hyunchul; Zubairy, M. Suhail
2016-06-01
The waveguide quantum electrodynamics (QED) system may have important applications in quantum device and quantum information technology. In this article we review the methods being proposed to calculate photon transport in a one-dimensional (1D) waveguide coupled to quantum emitters. We first introduce the Bethe ansatz approach and the input–output formalism to calculate the stationary results of a single photon transport. Then we present a dynamical time-dependent theory to calculate the real-time evolution of the waveguide QED system. In the longtime limit, both the stationary theory and the dynamical calculation give the same results. Finally, we also briefly discuss the calculations of the multiphoton transport problems.
One-step multi-qubit GHZ state generation in a circuit QED system
Wang, Ying-Dan; Loss, Daniel; Bruder, Christoph
2009-01-01
We propose a one-step scheme to generate GHZ states for superconducting flux qubits or charge qubits in a circuit QED setup. The GHZ state can be produced within the coherence time of the multi-qubit system. Our scheme is independent of the initial state of the transmission line resonator and works in the presence of higher harmonic modes. Our analysis also shows that the scheme is robust to various operation errors and environmental noise.
Dong, Dong; Zhang, Yan-Lei; Zou, Chang-Ling, E-mail: clzou321@ustc.edu.cn; Zou, Xu-Bo, E-mail: xbz@ustc.edu.cn; Guo, Guang-Can
2015-10-09
We propose an experimental feasible scheme for implementing two-qubit quantum phase gate with atoms trapped in an optical cavity. The scheme is based on the dispersive interaction between the optical cavity mode and the three-level atoms in Λ configuration, which has been demonstrated in recent cavity-induced spin squeezing experiment (Leroux et al., 2010) [26]. We also discuss the influence of the cavity decay on the gate fidelity. It is shown that the fidelity of the phase gate is robust to the cavity decay and the high-fidelity quantum phase gate can be implemented with the current experimental technology. - Highlights: • A experimental feasible scheme for implementing two-qubit quantum phase gate. • Based on the dispersive interaction between the optical cavity mode and the symmetrically configurated three-level atoms. • Influence of the cavity decay on the gate fidelity is discussed.
From strong to ultrastrong coupling in circuit QED architectures
Niemczyk, Thomas
2011-08-10
The field of cavity quantum electrodynamics (cavity QED) studies the interaction between light and matter on a fundamental level: a single atom interacts with a single photon. If the atom-photon coupling is larger than any dissipative effects, the system enters the strong-coupling limit. A peculiarity of this regime is the possibility to form coherent superpositions of light and matter excitations - a kind of 'molecule' consisting of an atomic and a photonic contribution. The novel research field of circuit QED extends cavity QED concepts to solid-state based system. Here, a superconducting quantum bit is coupled to an on-chip superconducting one-dimensional waveguide resonator. Owing to the small mode-volume of the resonant cavity, the large dipole moment of the 'artificial atom' and the enormous engineering potential inherent to superconducting quantum circuits, remarkable atom-photon coupling strengths can be realized. This thesis describes the theoretical framework, the development of fabrication techniques and the implementation of experimental characterization techniques for superconducting quantum circuits for circuit QED applications. In particular, we study the interaction between superconducting flux quantum bits and high-quality coplanar waveguide resonators in the strong-coupling limit. Furthermore, we report on the first experimental realization of a circuit QED system operating in the ultrastrong-coupling regime, where the atom-photon coupling rate reaches a considerable fraction of the relevant system frequencies. In these experiments we could observe phenomena that can not be explained within the renowned Jaynes-Cummings model. (orig.)
High-Q AlAs/GaAs adiabatic micropillar cavities with submicron diameters for cQED experiments
Lermer, M.; Gregersen, Niels; Dunzer, F.; Mørk, Jesper; Reitzenstein, S.; Höfling, S.; Kamp, M.; Forchel, A.
microcavity design [1, 2]. To overcome the trade-off between high Q and low Vmode, we designed and implemented a novel adiabatic AlAs/GaAs cavity design (MC1) with 3 taper segments (Fig. 1 (a)) as it was suggested by Zhang et al. for SiO2/TiO2 micropillar cavities [3]. Comparative measurements of the Q factor...
We propose a scheme to realize the optimal economical 1->2 phase-covariant quantum cloning machine (QCM) in 2 dimension with superconducting quantum interference device (SQUID) qubits in a microwave cavity. In our scheme, two-SQUID qubits are fixed into a microwave cavity by adiabatic passage method for their manipulation. Using this method, we can realize the optimal phase-covariant QCM only by one step
RF cavity vacuum interlock system
Jordan, K.; Crawford, K.; Bundy, R.; Dylla, H. F.; Heckman, J.; Marshall, J.; Nichols, R.; Osullivan, S.; Preble, J.; Robb, J.
1992-03-01
The Continuous Electron Beam Accelerator Facility (CEBAF), a continuous wave (CW) 4 GeV Electron Accelerator is undergoing construction in Newport News, Virginia. When completed in 1994, the accelerator will be the largest installation of radio-frequency superconductivity. Production of cryomodules, the fundamental building block of the machine, has started. A cryomodule consists of four sets of pairs of 1497 MHz, 5 cell niobium cavities contained in separate helium vessels and mounted in a cryostat with appropriate end caps for helium supply and return. Beam vacuum of the cavities, the connecting beam piping, the waveguides, and the cryostat insulating vacuum are crucial to the performance of the machine. The design and initial experience of the vacuum systems for the first 2 1/4 cryomodules that makeup the 45 MEV injector are discussed.
PREFACE: Heavy-Ion Spectroscopy and QED Effects in Atomic Systems
Lindgren, Ingvar; Martinson, Indrek; Schuch, Reinhold
1993-01-01
Experimental studies of heavy and highly charged ions have made remarkable progress in recent years. Today it is possible to produce virtually any ion up to hydrogen-like uranium; to study collisions of those ions with atoms, electrons, and solid surfaces; to excite such an ion and accurately measure the radiation emitted. This progress is largely due to the development of new experimental methods, for instance, the high-energy ion accelerators, laser-produced plasmas, advanced ion sources and ion traps (such as EBIS, EBIT, ECR, etc.), high temperature magnetically confined plasmas and heavy-ion storage rings. The motivations for studies of collisions with highly charged ions and for the understanding of the structure of heavy atomic systems are multi-faceted. Besides of the basic scientific aspects which are mainly the subject of this symposium, much incentive is experienced by applications, e.g., the interpretation of spectra from space (solar corona, solar flares and hot stars), the modelling of stellar atmospheres, the diagnostics of fusion plasma impurities, and the development of X-ray lasers. Since quite some time highly charged ions play a key role for high-precision metrology of atomic structure. These studies have been benchmarks for tests of advanced theories, including many-body theories of interelectronic correlations, relativistic and quantum-electrodynamic (QED) effects, effects due to the finite size of the nucleus and to parity non-conservation (PNC). The interest in QED effects in heavy ions has increased drastically in the last few years. The remarkable experiment on Li-like uranium, recently reported from Berkeley, has stimulated several groups to perform very accurate Lamb-shift calculations on such systems, and reports from three groups were given about such work. The agreement between the calculations as well as with experiment was generally very good, which implies that the problem of evaluating the first-order Lamb shift for any element is
The QED engine system: Direct-electric fusion-powered rocket propulsion systems
Practical ground-to-orbit and inter-orbital space flights both require propulsion systems of large flight-path-averaged specific impulse (Isp) and engine system thrust-to-mass-ratio (F/me=[F]) for useful payload and structure fractions in single-stage vehicles (Hunter 1966). Current rocket and air-breathing engine technologies lead to enormous vehicles and small payloads; a natural result of the limited specific energy available from chemical reactions. While nuclear energy far exceeds these specific energy limits (Bussard and DeLauer 1958), the inherent high-Isp advantages of fission propulsion concepts for space and air-breathing flight (Bussard and DeLauer 1965) are negated for manned systems by the massive radiation shielding required by their high radiation output (Bussard 1971). However, there are well-known radiation-free nuclear fusion reactions (Gross 1984) between isotopes of selected light elements (such as H+11B, D+3He) that yield only energetic charged particles, whose energy can be converted directly into electricity by confining electric fields (Moir and Barr 1973,1983). New confinement concepts using magnetic-electric-potentials (Bussard 1989a) or inertial-collisional-compression (ICC) (Bussard 1990) have been found that offer the prospect of clean, compact fusion systems with very high output and low mass. Their radiation-free d.c. electrical output can power unique new electron-beam-driven thrust systems of extremely high performance. Parametric design studies show that such charged-particle electric-discharge engines (''QED'' engines) might yield rocket propulsion systems with performance in the ranges of 2sp<5500 sec
Full text: We perform the stochastic quantization of scalar as well as of fermionic QED based on a generalization of the stochastic gauge fixing scheme and its geometrical interpretation. It is shown that the stochastic quantization scheme agrees exactly with the usual path integral formulation. (author)
Von starker zu ultrastarker Kopplung in Schaltkreis QED Architekturen
Niemczyk, Thomas
2011-01-01
Das Forschungsgebiet der Hohlraum-Quantenelektrodynamik (cavity QED) untersucht die Wechselwirkung zwischen Licht und Materie auf fundamentaler Ebene: ein einzelnes Atom wechselwirkt mit einem einzelnen Photon. Falls die Atom-Photon Kopplung stärker ist als alle anderen dissipativen Effekte, befindet sich das System im sogenannten Regime starker Kopplung. Eine Besonderheit dieses Regimes besteht in der Möglichkeit der Formierung eines kohärenten Superpositionszustands aus Licht- und Materiean...
SPS RF System an Accelerating Cavity
1975-01-01
The picture shows one of the two initially installed cavities. The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities. Initially only two cavities were installed, a third cavity was installed in 1978 and a forth one in 1979. The number of power amplifiers was also gradually increased: by end 1980 there were 8 500 kW units combined in pairs to feed each of the 4 cavities with up to about 1 MW RF power, resulting in a total accelerating voltage of about 8 MV. See also 7412017X, 7411048X.
Spallation neutron source RF cavity bias system
The Spallation Neutron Source r.f. cavity bias system is described under the topic headings: bias system, r.f. cavity, cables, d.c. bias power supply, transistor regulator and control system. Calculation of 4 core 300 mm solid aluminium cable inductance, coaxial shunt frequency response and transistor regulator computed frequency response, are discussed in appendices 1-3. (U.K.)
Testing quantum nonlocality for three coupled quantum dots within optical microcavity QED
Moradi, Shahpoor
2012-01-01
Bell's inequality in three coupled quantum dots (QDs) within cavity QED, including Forster and exciton-phonon interactions, is investigated theoretically. For an initially entangled state, Bell's inequality is valid for certain times and violated for some other times. It is shown that the system moves from a product state to a entangled state and back again during it's time evolution.
Theory of implementation of an impedance-matched Λ system in circuit QED
Koshino, Kazuki; Inomata, Kunihiro; Yamamoto, Tsuyoshi; Nakamura, Yasunobu
2014-03-01
In one-dimensional optical setups, light-matter interaction is drastically enhanced by the interference between the incident and scattered fields. Particularly, in an impedance-matched Λ-type three-level system, which has two identical radiative decay rates from the top level and interacts with a semi-infinite one-dimensional field in reflection geometry, a single photon deterministically induces the Raman transition and switches the electronic state of the system. Here we theoretically investigate a circuit QED system composed of a driven superconducting qubit and a resonator in the dispersive regime. We show that the dressed states of this system constitute an impedance-matched Λ system under a proper choice of the frequency and power of the qubit drive. When we apply a resonant probe field to this system, it is down-converted nearly perfectly after a single reflection as long as the probe power is sufficiently weak. This indicates a deterministic quantum dynamics induced by single photons, which is applicable, for example, to the detection of single microwave photons and the bidirectional quantum memory (swapping) between a microwave photon and a superconducting qubit. This work was partly supported by FIRST, MEXT KAKENHI (21102002 and 25400417), SCOPE (111507004) and NICT.
Nielsen, Per Kær; Nielsen, Torben Roland; Lodahl, Peter;
2010-01-01
treatments. A pronounced consequence is the emergence of a phonon induced spectral asymmetry when detuning the cavity from the quantum-dot resonance. The asymmetry can only be explained when considering the polaritonic quasiparticle nature of the quantum-dot-cavity system. Furthermore, a temperature induced......We investigate the influence of electron-phonon interactions on the dynamical properties of a quantum-dot-cavity QED system. We show that non-Markovian effects in the phonon reservoir lead to strong changes in the dynamics, arising from photon-assisted dephasing processes, not present in Markovian...
Design of the ILC Crab Cavity System
Adolphsen, C.; Beard, C.; Bellantoni, L.; Burt, G.; Carter, R.; Chase, B.; Church, M.; Dexter, A.; Dykes, M.; Edwards, H.; Goudket, P; Jenkins, R.; Jones, R.M.; Kalinin,; Khabiboulline, T.; Ko, K.; Latina, A.; Li, Z.; Ma, L.; McIntosh, P.; Ng, C.; /SLAC /Daresbury /Fermilab /Cockcroft Inst. Accel. Sci. Tech. /CERN
2007-08-15
The International Linear Collider (ILC) has a 14 mrad crossing angle in order to aid extraction of spent bunches. As a result of the bunch shape at the interaction point, this crossing angle at the collision causes a large luminosity loss which can be recovered by rotating the bunches prior to collision using a crab cavity. The ILC baseline crab cavity is a 9-cell superconducting dipole cavity operating at a frequency of 3.9 GHz. In this paper the design of the ILC crab cavity and its phase control system, as selected for the RDR in February 2007 is described in fuller detail.
Design of the ILC Crab Cavity System
The International Linear Collider (ILC) has a 14 mrad crossing angle in order to aid extraction of spent bunches. As a result of the bunch shape at the interaction point, this crossing angle at the collision causes a large luminosity loss which can be recovered by rotating the bunches prior to collision using a crab cavity. The ILC baseline crab cavity is a 9-cell superconducting dipole cavity operating at a frequency of 3.9 GHz. In this paper the design of the ILC crab cavity and its phase control system, as selected for the RDR in February 2007 is described in fuller detail
Giant photon gain in large-scale quantum dot circuit-QED systems
Agarwalla, Bijay Kumar; Mukamel, Shaul; Segal, Dvira
2016-01-01
Motivated by recent experiments on the generation of coherent light in engineered hybrid quantum systems, we investigate gain in a microwave photonic cavity coupled to quantum dot structures, and develop concrete directions for achieving a giant amplification in photon transmission. We propose two architectures for scaling up the electronic gain medium: (i) $N$ double quantum dot systems (N-DQD), (ii) $M$ quantum dots arranged in series akin to a quantum cascade laser setup. In both setups, the fermionic reservoirs are voltage biased, and the quantum dots are coupled to a single-mode cavity. Optical amplification is explained based on a sum rule for the transmission function, and it is determined by an intricate competition between two different processes: charge density response in the gain medium, and cavity losses to input and output ports. The same design principle is also responsible for the corresponding giant amplification in other photonic observables, mean photon number and emission spectrum, thereby...
Probing phases of interacting polaritons in circuit QED setups
Circuit QED systems pose a new paradym for reaching the strong coupling regime of photonic and atomic degrees of freedom and are thus ideal candidates for quantum simulation and computation. We are investigating one-dimensional arrays of transmission-line cavities, where each cavity is coupled to a transmon-qubit. This system can be used as a quantum many-body simulator, lowering the experimental requirements for prescission control with respect to the use as a quantum computing device. We exploit the intermediate qubit-harmonic oscillator regime of the transmon to simulate Bose-Hubbard physics. As a suitable experimental setup we consider a system where the first cavity is driven by a classical microwave source and the output voltage is monitored, with respect to signatures of a quantum phase transition, at the last cavity.
Drummond, I T
2016-01-01
We study, as a model of Lorentz symmetry breaking, the quantisation and renormalisation of an extension of QED in a flat spacetime where the photons and electrons propagate differently and do not share the same lightcone. We will refer to this model as Bimetric QED (BIMQED). As a preliminary we discuss the formulation of electrodynamics in a pre-metric formalism showing nevertheless that there is, on the basis of a simple criteron, a preferred metric. Arising from this choice of metric is a Weyl-like tensor (WLT). The Petrov classification of the WLT gives rise to a corresponding classification of Lorentz symmetry breaking. We do not impose any constraint on the strength of the symmetry breaking and are able to obtain explicit dispersion relations for photon propagation in each of the Petrov classes. The associated birefringence appears in some cases as two distinct polarisation dependent lightcones and in other cases as a a more complicated structure that cannot be disentangled in a simple way. We show how i...
Calderón Losada, Omar
2010-01-01
Se estudia un método para generar enredamiento entre dos átomos que atraviesan secuencialmente una cavidad cuántica electrodinámica (cQED) mediante interacciones átomo-campo en las que se intercambian un fotón o dos fotones. Se analizan las condiciones bajo las cuales es válido el hamiltoniano para el caso de intercambio de dos fotones, que se construye empleando la teoría de perturbaciones independiente del tiempo. Se muestra que, cuando dos átomos que atraviesan secuencialmente el campo de ...
Shallow Cavities in Multiple-Planet Systems
Duffell, Paul C.; Dong, Ruobing
2014-01-01
Large cavities are often observed in protoplanetary disks, which might suggest the presence of planets opening gaps in the disk. Multiple planets are necessary to produce a wide cavity in the gas. However, multiple planets may also be a burden to the carving out of very deep gaps. When additional planets are added to the system, the time-dependent perturbations from these additional satellites can stir up gas in the gap, suppressing cavity opening. In this study, we perform two-dimensional nu...
Atom-field dressed states in slow-light waveguide QED
Calajó, Giuseppe; Ciccarello, Francesco; Chang, Darrick; Rabl, Peter
2016-03-01
We discuss the properties of atom-photon bound states in waveguide QED systems consisting of single or multiple atoms coupled strongly to a finite-bandwidth photonic channel. Such bound states are formed by an atom and a localized photonic excitation and represent the continuum analog of the familiar dressed states in single-mode cavity QED. Here we present a detailed analysis of the linear and nonlinear spectral features associated with single- and multiphoton dressed states and show how the formation of bound states affects the waveguide-mediated dipole-dipole interactions between separated atoms. Our results provide both a qualitative and quantitative description of the essential strong-coupling processes in waveguide QED systems, which are currently being developed in the optical and microwave regimes.
Inertial confinement fusion (ICF) embodies the simultaneous firing of large-scale multiple high intensity mega-joule laser pulses at targets of pea-sized deuterium pellets. Fusion is initiated on the premise that temperatures over 100 million degrees and density 1000x normal solid density are produced in pellet implosion. Contrary to large scale ICF reactor designs, neutrons were recently found in Berlin with a significantly down-sized table-top system using a 815 nm laser depositing ∼ 35 femto-second pulses of 120 milli-joules to a spray of submicron droplets of heavy water. Ionization of the D2O is thought to leave the submicron droplets with charged D2O+ ions as the electrons rapidly escape at which time the droplets undergo Coulomb explosions. Neutrons are produced in the collisions of the D2O+ ions with those emitted from neighboring droplets. Although a convenient source of submicron D2O droplets, the spray lacks containment of the Coulomb explosion to produce the high pressures necessary to significantly increase neutron yield. A containment shell encapsulating the D2O is proposed here to briefly increase the pressure by confining the D2O+ ions in the Coulomb explosion. In pea-sized targets this is not possible because the shell would vaporize under the high temperatures necessary for implosion. But with submicron targets, the temperature does not increase during the absorption of the laser photons because of the quantum electrodynamics (QED) confinement of the electromagnetic (EM) radiation.. Specifically, IR radiation from absorbed photons is precluded having half-wavelengths larger than the target diameter, or equivalently any increase in target temperature that accompanies the IR radiation is forbidden. What this means is that in pea-sized targets large in relation to the half-IR wavelength, the deposition of laser energy is allowed to be conserved by an increase in temperature; whereas, in submicron targets far smaller than the respective half
Ion-cavity system for quantum networks
Full text: A single atom interacting with a single mode of a cavity allows us to probe the quantum interaction between light and matter. In the context of quantum networks, such a system can provide an interface between stationary and flying qubits, making it possible for single photons to transport quantum information between the network nodes. We study a single 40Ca+ ion trapped inside a high-finesse optical resonator. First, we demonstrate and characterize a single-photon source, in which a vacuum-stimulated Raman process transfers atomic population between two Zeeman states of the ion, creating a single photon in the cavity. We evaluate the photon statistics by measuring the second-order correlation function. Moreover, we obtain the photon temporal profile and investigate the dynamics of the process. Secondly, we perform Raman spectroscopy using the cavity. Residual motion of the ion introduces motional sidebands in the Raman spectrum and thus offers prospects for cavity-assisted cooling. (author)
Cryogenic system for TRISTAN superconducting RF cavity
Superconducting RF cavities will be installed in TRISTAN at KEK to upgrade the electron-positron beam energy to 33 GeV x 33 GeV. Two 5-cell cavities are coupled together, enclosed in a cryostat, and cooled by liquid helium pool boiling. The cryogenic system for the cavities is described and a system flow diagram constructed. Heat loads are estimated and component specifications are given. The capacity of the helium refrigerator is 4 kW at 4.4 K with liquid nitrogen precooling and two expansion turbines. The system is designed to be upgraded to 6.5 kW with added expansion turbines and compressors and the elimination of liquid nitrogen
Polariton states in circuit QED for electromagnetically induced transparency
Gu, Xiu; Huai, Sai-Nan; Nori, Franco; Liu, Yu-xi
2016-06-01
Electromagnetically induced transparency (EIT) has been extensively studied in various systems. However, it is not easy to observe in superconducting quantum circuits (SQCs) because the Rabi frequency of the strong-controlling field corresponding to EIT is limited by the decay rates of the SQCs. Here, we show that EIT can be achieved by engineering decay rates in a superconducting circuit QED system through a classical driving field on the qubit. Without such a driving field, the dressed states of the system, describing a superconducting qubit coupled to a cavity field, are approximately product states of the cavity and qubit states in the large-detuning regime. However, the driving field can strongly mix these dressed states. These doubly dressed states, here called polariton states, are formed by the driving field and dressed states, and are a mixture of light and matter. The weights of the qubit and cavity field in the polariton states can now be tuned by the driving field, and thus the decay rates of the polariton states can be changed. We choose the three lowest-energy polariton states with a Λ -type transition in such a driven circuit QED system, and demonstrate how EIT and Autler-Townes splitting can be realized in this compound system. We believe that this study will be helpful for EIT experiments using SQCs.
A microelectromechanically controlled cavity optomechanical sensing system
Miao, Houxun; Aksyuk, Vladimir
2012-01-01
Microelectromechanical systems (MEMS) have been applied to many measurement problems in physics, chemistry, biology and medicine. In parallel, cavity optomechanical systems have achieved quantum-limited displacement sensitivity and ground state cooling of nanoscale objects. By integrating a novel cavity optomechanical structure into an actuated MEMS sensing platform, we demonstrate a system with high quality-factor interferometric readout, electrical tuning of the optomechanical coupling by two orders of magnitude, and a mechanical transfer function adjustable via feedback. The platform separates optical and mechanical components, allowing flexible customization for specific scientific and commercial applications. We achieve displacement sensitivity of 4.6 fm/Hz^1/2 and force sensitivity of 53 aN/Hz^1/2 with only 250 nW optical power launched into the sensor. Cold-damping feedback is used to reduce the thermal mechanical vibration of the sensor by 3 orders of magnitude and to broaden the sensor bandwidth by a...
Optical cavity and transport system for FELI
FELI (Free Electron Laser Research Institute, Inc.) is aiming at FIR-, IR-, VISIBLE-, and UV-FEL (spectral range from 0.3 to 22.7μm) generation using 30-, 75-, 120-, 165-MeV beams, respectively. The linear accelerator and four undulators are installed in the ground floor and five FEL users rooms are located in the third floor, so the longest FEL transport pass is about 80m long. We will adopt hole out coupling for FIR- and IR-FEL optical cavities. The output beam is collimated by an inverted telescope and transported to the users rooms via N2 purged pipes. Achieving optical beam stability and quality are primary concerns. For keeping optical beam stability and quality, a beam axis control unit and a position monitoring system are used. These optical cavities and FEL transport systems are under construction and will be used for FIR- and IR-FEL experiments in this summer. (author)
Quantum Dynamics of Nonlinear Cavity Systems
Nation, Paul D
2010-01-01
We investigate the quantum dynamics of three different configurations of nonlinear cavity systems. To begin, we carry out a quantum analysis of a dc superconducting quantum interference device (SQUID) mechanical displacement detector comprised of a SQUID with a mechanically compliant loop segment. The SQUID is approximated by a nonlinear current-dependent inductor, inducing a flux tunable nonlinear Duffing term in the cavity equation of motion. Expressions are derived for the detector signal and noise response where it is found that a soft-spring Duffing self-interaction enables a closer approach to the displacement detection standard quantum limit, as well as cooling closer to the ground state. Next, we make use of a superconducting transmission line formed from an array of dc-SQUIDs for investigating analogue Hawking radiation. Biasing the array with a space-time varying flux modifies the propagation velocity of the transmission line, leading to an effective metric with a horizon. This setup allows for quan...
Luo, Yongjiang; Li, Lijia; Peng, Jianming; Yin, Kun; Li, Peng; Gan, Xin; Zhao, Letao; Su, Wei
2015-12-01
The subterranean cavities are seriously threatened to construction and mining safety, and it's important to obtain the exact localization and dimensions of subterranean cavities for the planning of geotechnical and mining activities. Geophysical investigation is an alternative method for cavity detection, but it usually failed for the uncertainly solution of information and data obtained by Geophysical methods. Drilling is considered as the most accurate method for cavity detection. However, the conventional drilling methods can only be used for single cavity detection, and there is no effective solution for multilayer cavities detection have been reported. In this paper, a reverse circulation (RC) down-the-hole (DTH) air hammer system with a special structured drill bit is built and a cavity auto scanning laser system based on laser range finding technique was employed to confirm the localization and dimensions of the cavities. This RC-DTH air hammer system allows drilling through the upper cavities and putting the cavity auto scanning laser system into the cavity area through the central passage of the drill tools to protect the detection system from collapsing of borehole wall. The RC-DTH air hammer system was built, and field tests were conducted in Lanxian County Iron Ore District, which is located in Lv Liang city of Shan Xi province, the northwest of china. Field tests show that employing the RC-DTH air hammer system assisted by the cavity auto scanning laser system is an efficiency method to detect multilayer cavities.
We present measurements and modelling of the susceptibility of a 2D microstrip cavity coupled to a driven transmon qubit. We are able to fit the response of the cavity to a weak probe signal with high accuracy in the strong coupling, low detuning, i.e., non-dispersive, limit over a wide bandwidth. The observed spectrum is rich in multi-photon processes for the doubly dressed transmon. These features are well explained by including the higher transmon levels in the driven Jaynes–Cummings model and solving the full master equation to calculate the susceptibility of the cavity. (paper)
Development of oral cavity inspecting system
Zhang, Hongxia; Wu, Di; Jia, Dagong; Zhang, Yimo
2009-11-01
An oral cavity inspecting system is designed and developed to inspect the detail of teeth. The inspecting system is composed of microscopic imaging part, illuminating part, image capture and processing, display part. The two groups of cemented lenses were optimized to minimize the optical aberration and the collimated beam light is gotten between the two lenses. A relay lens is adopted to allow the probe to access the oral cavity depth. The illumination optic fiber is used and the brightness and color temperature can be adjustable. The illumination fiber end surface is oblique cut and the optimum angle is 37°. The image of teeth is imaged on CMOS and captured into computer. The illumination intensity and uniformity were tested and the proper parameter is set. Foucault chart was observed and the system resolution is higher than 100lp/mm. The oral inspecting system is used to test standard tooth model and patho-teeth model. The tooth image is clear and the details can be observed. The experimental results show that the system could meet dental medical application requirements.
Ruesink, Freek; Doeleman, Hugo M; Hendrikx, Ruud; Koenderink, A Femius; Verhagen, Ewold
2015-11-13
The influence of a small perturbation on a cavity mode plays an important role in fields like optical sensing, cavity quantum electrodynamics, and cavity optomechanics. Typically, the resulting cavity frequency shift directly relates to the polarizability of the perturbation. Here, we demonstrate that particles perturbing a radiating cavity can induce strong frequency shifts that are opposite to, and even exceed, the effects based on the particles' polarizability. A full electrodynamic theory reveals that these anomalous results rely on a nontrivial phase relation between cavity and nanoparticle radiation, allowing backaction via the radiation continuum. In addition, an intuitive model based on coupled mode theory is presented that relates the phenomenon to retardation. Because of the ubiquity of dissipation, we expect these findings to benefit the understanding and engineering of a wide class of systems. PMID:26613442
Beam commissioning of KEKB crab cavity RF system
KEKB started the first crab crossing operation in February 2007 with two superconducting crab cavities. After four months operation dedicated for machine tuning, physics run with high-current beams resumed in October with the crab crossing. The crab cavities have been working stably for one and a half years. The crab cavity RF system, commissioning process and performance of the crab cavities with high-current beams are presented. (author)
Precision Study of Positronium: Testing Bound State QED Theory
Karshenboim, Savely G.
2003-01-01
As an unstable light pure leptonic system, positronium is a very specific probe atom to test bound state QED. In contrast to ordinary QED for free leptons, the bound state QED theory is not so well understood and bound state approaches deserve highly accurate tests. We present a brief overview of precision studies of positronium paying special attention to uncertainties of theory as well as comparison of theory and experiment. We also consider in detail advantages and disadvantages of positro...
We propose a simple scheme to realize 1→M economical phase-covariant quantum cloning machine (EPQCM) with superconducting quantum interference device (SQUID) qubits. In our scheme, multi-SQUIDs are fixed into a microwave cavity by adiabatic passage for their manipulation. Based on this model, we can realize the EPQCM with high fidelity via adiabatic quantum computation
... the bacteria produce acids that cause decay. Tooth pain occurs after decay reaches the inside of the tooth. Dentists can detect cavities by examining the teeth and taking x-rays periodically. Good oral hygiene and regular dental care plus a healthy diet can help prevent cavities. ...
Photon-photon interactions with inner coupled double-cavity
Lai Wen-Xi; Li Hong-Cai; Yang Rong-Can
2008-01-01
This paper describes the interaction between two spatial modes of the optical fields with a single atom trapped inner coupled double-cavity.Theoretical derivation and numerical simulation with the experimental available parameters show that photon-photon switching and π phase shift of single photons may be achieved with current experimental technology.As the probe and control fields are in different spatial modes,the system is superior for implementing cavity QED-based photonic quantum networks.
In this paper we present a method to engineer the unitary charge conjugation operator, as given by quantum field theory, in the highly controlled context of quantum optics, thus allowing one to simulate the creation of charged particles with well-defined momenta simultaneously with their respective antiparticles. Our method relies on trapped ions driven by a laser field and interacting with a single mode of a light field in a high Q cavity. (paper)
Photon-assisted tunnelling with nonclassical microwaves in hybrid circuit QED systems
Souquet, Jean-René; Woolley, Matthew; Gabelli, Julien; Simon, Pascal; Clerk, Aashish
2015-03-01
Motivated by recent experiments where superconducting microwave circuits have been coupled to electrons in semiconductor nanostructures, we study theoretically the interplay of non-classical light produced in a cavity with electron transport through a tunnel junction. We demonstrate that this basic light-matter interaction is naturally characterized by non-positive definite quasi-probability distributions which are intimately connected to the Glauber-Sudarshan P-function. We further demonstrate that this negative quasiprobability has unequivocal signatures on the differential conductance that should be easily detectable in state of art experiments. This thus turns the tunnel junction into a non-trivial probe of the microwave state. We also discuss the non-trivial backaction of the junction current on the cavity.
The lecture concerns quantum electrodynamics (QED), the relativistic quantum theory of electromagnetic interactions. Antiparticles, electrodynamics of spinless particles, the dirac equation and electrodynamics of spin 1/2 particles are discussed in detail. (U.K.)
Interacting Photons in Waveguide-QED and Applications in Quantum Information Processing
Zheng, Huaixiu
Strong coupling between light and matter has been demonstrated both in classical cavity quantum electrodynamics (QED) systems and in more recent circuit-QED experiments. This enables the generation of strong nonlinear photon-photon interactions at the single-photon level, which is of great interest for the observation of quantum nonlinear optical phenomena, the control of light quanta in quantum information protocols such as quantum networking, as well as the study of strongly correlated quantum many-body systems using light. Recently, strong coupling has also been realized in a variety of one-dimensional (1D) waveguide- QED experimental systems, which in turn makes them promising candidates for quantum information processing. Compared to cavity-QED systems, there are two new features in waveguide-QED: the existence of a continuum of states and the restricted 1D phase space, which together bring in new physical effects, such as the bound-state effects. This thesis consists of two parts: 1) understanding the fundamental interaction between local quantum objects, such as two-level systems and four-level systems, and photons confined in the waveguide; 2) exploring its implications in quantum information processing, in particular photonic quantum computation and quantum key distribution. First, we demonstrate that by coupling a two-level system (TLS) or three/four-level system to a 1D continuum, strongly-correlated photons can be generated inside the waveguide. Photon-photon bound states, which decay exponentially as a function of the relative coordinates of photons, appear in multiphoton scattering processes. As a result, photon bunching and antibunching can be observed in the photon-photon correlation function, and nonclassical light source can be generated on demand. In the case of an N-type four-level system, we show that the effective photon-photon interaction mediated by the four-level system, gives rise to a variety of nonlinear optical phenomena, including
Cavity parameters identification for TESLA control system development
The control system modeling for the TESLA - TeV-Energy Superconducting Linear Accelerator project has been developed for the efficient stabilization of the pulsed, accelerating EM field of the resonator. The cavity parameters identification is an essential task for the comprehensive control algorithm. The TESLA cavity simulator has been successfully implemented by applying very high speed FPGA - Field Programmable Gate Array technology. The electromechanical model of the cavity resonator includes the basic features - Lorentz force detuning and beam loading. The parameters identification bases on the electrical model of the cavity. The model is represented by the state space equation for the envelope of the cavity voltage driven by the current generator and the beam loading. For a given model structure, the over-determined matrix equation is created covering the long enough measurement range with the solution according to the least squares method. A low degree polynomial approximation is applied to estimate the time-varying cavity detuning during the pulse. The measurement channel distortion is considered, leading to the external cavity model seen by the controller. The comprehensive algorithm of the cavity parameters identification has been implemented in the Matlab system with different modes of the operation. Some experimental results have been presented for different cavity operational conditions. The following considerations have lead to the synthesis of the efficient algorithm for the cavity control system predicted for the potential FPGA technology implementation. (orig.)
Renormalization of QED near Decoupling Temperature
Masood, Samina S
2014-01-01
We study the effective parameters of QED near decoupling temperatures and show that the QED perturbative series is convergent, at temperatures below the decoupling temperature. The renormalization constant of QED acquires different values if a system cools down from a hotter system to the electron mass temperature or heats up from a cooler system to the same temperature. At T = m, the first order contribution to the electron selfmass, {\\delta}m/m is 0.0076 for a heating system and 0.0115 for a cooling system and the difference between two values is equal to 1/3 of the low temperature value and 1/2 of the high temperature value around T~m. This difference is a measure of hot fermion background at high temperatures. With the increase in release of more fermions at hotter temperatures, the fermion background contribution dominates and weak interactions have to be incorporated to understand the background effects.
Cavity Ring-down Spectroscopic System And Method
Alquaity, Awad Bin Saud
2015-05-14
A system and method for cavity ring-down spectroscopy can include a pulsed quantum cascade laser, an optical ring-down cavity, a photodetector, and an oscilloscope. The system and method can produce pulse widths of less than 200 ns with bandwidths greater than 300 pm, as well as provide temporal resolution of greater than 10 .mu.s.
Reactor cavity cleanup system shielded filter installation
The Seabrook Station reactor cavity cleanup system provides a flow path for refueling pool purification and drain down during plant refueling evolutions. The original system design included refueling pool surface skimmers and drains, a skimmer pump, an unshielded duplex basket type pump suction strainer and interconnecting stainless steel piping. The piping design utilized socket welded joints in small bore pipe with diaphragm values installed in the horizontal pipe runs downstream of the skimmer pump. The previously installed unshielded strainer in addition to the skimmer pump downstream piping components were determined to be inconsistent with Seabrook's proactive approach to dose reduction. To be consistent with ALARA (As Low As Reasonably Achievable) policy, a plant design change was authorized to install a lead shielded filter unit as a replacement for the existing duplex strainer. This filter unit, which utilizes multiple micron rating disposable basket type cartridges, has a threefold function of protecting the skimmer pump from large solids, providing bulk filtration of activated corrosion products from the refueling water in order to minimize CRUD buildup in downstream components, and enabling retrieval of foreign material drawn into the refueling pool drains
Entangled Schrodinger cats in circuit QED: Experimental Architecture
Wang, Chen; Gao, Yvonne Y.; Reinhold, Philip; Heeres, Reinier W.; Ofek, Nissim; Chou, Kevin; Axline, Christopher; Frunzio, Luigi; Devoret, Michel H.; Schoelkopf, Robert J.
The development of quantum information technology relies on creating and controling entanglement over an increasingly large Hilbert space. Superconducting cavities offer high-dimensional spaces for quantum states in a low-loss and hardware-efficient fashion, making it an ideal memory of quantum information and an important element towards fault-tolerant quantum computation. In this talk we present a cQED architecture that allows quantum control over the coherent state basis of two superconducting cavities with millisecond coherence. In particular, we show deterministic entanglement of coherent-state microwave fields in two superconducting cavities of the form: 1/√{ 2}" open="" separators="">βa" open="" separators="">βa +/- -" open="" separators="">βa -" open="" separators="">βa . We engineer the capability to measure the joint photon number parity to achieve complete state tomography of the two-cavity state. Following widespread efforts of realizing ``Schrodinger's cat''-like mesoscopic superposition in various physical systems, this experiment demonstrates mesoscopic entanglement between two ``Schrodinger's cats''.
Quantum memory with millisecond coherence in circuit QED
Reagor, Matthew; Pfaff, Wolfgang; Axline, Christopher; Heeres, Reinier W.; Ofek, Nissim; Sliwa, Katrina; Holland, Eric; Wang, Chen; Blumoff, Jacob; Chou, Kevin; Hatridge, Michael J.; Frunzio, Luigi; Devoret, Michel H.; Jiang, Liang; Schoelkopf, Robert J.
2016-07-01
Significant advances in coherence render superconducting quantum circuits a viable platform for fault-tolerant quantum computing. To further extend capabilities, highly coherent quantum systems could act as quantum memories for these circuits. A useful quantum memory must be rapidly addressable by Josephson-junction-based artificial atoms, while maintaining superior coherence. We demonstrate a superconducting microwave cavity architecture that is highly robust against major sources of loss that are encountered in the engineering of circuit QED systems. The architecture allows for storage of quantum superpositions in a resonator on the millisecond scale, while strong coupling between the resonator and a transmon qubit enables control, encoding, and readout at MHz rates. This extends the maximum available coherence time attainable in superconducting circuits by almost an order of magnitude compared to earlier hardware. Our design is an ideal platform for studying coherent quantum optics and marks an important step towards hardware-efficient quantum computing in Josephson-junction-based quantum circuits.
Cavity cooling and normal-mode spectroscopy of a bound atom-cavity system
Full text: Single atoms strongly coupled to the field of an optical cavity form an attractive system for the realization of an atom-light interface useful for quantum information protocols. An experimental implementation of these schemes requires atoms which are trapped, cooled and localized in the cavity mode at a region of strong coupling. In the experiment presented here, single atoms are trapped and stored in a far-detuned intracavity dipole trap. We demonstrate cavity cooling by illuminating the system with a weak, slightly blue-detuned light beam. This extends the storage time of an atom, which is limited by parametric heating from fluctuations of the intracavity dipole trap, by more than a factor of two. The observed cooling force is of Sisyphus-type and was predicted. A special feature of this force is that it does not rely on the spontaneous emission of a photon by the atom, and therefore the cooling force is at least five times larger than the force achievable for free-space cooling methods with comparable excitation of a two-level atom. Preparing single atoms strongly-coupled to the mode of a high-finesse cavity in this way, we observe two well-resolved normal-mode peaks both in transmission of the cavity as well as in the trap lifetime. The experimental data agree well with a Monte Carlo simulation, demonstrating the localization of the atom to within a tenth of a wavelength at a cavity antinode. The ability to individually excite the normal modes of a bound atom-cavity system shows that we have reached good control over this fundamental quantum system. (author)
Petrov, E Yu
2016-01-01
The problem of longitudinal oscillations of an electric field and a charge polarization density in QED vacuum is considered. Within the framework of semiclassical analysis, we calculate time-periodic solutions of bosonized 1+1 dimensional QED (massive Schwinger model). Applying the Bohr--Sommerfeld quantization condition, we determine the mass spectrum of charge-zero bound states (plasmons) which correspond in quantum theory to the found classical solutions. We show that the existence of such plasmons does not contradict any fundamental physical laws and study qualitatively their excitation in 3+1 dimensional real world.
The Test of LLRF control system on superconducting cavity
Zhu, Zhenglong; Wen, Lianghua; Chang, Wei; Zhang, Ruifeng; Gao, Zheng; Chen, Qi
2014-01-01
The first generation Low-Level radio frequency(LLRF) control system independently developed by IMPCAS, the operating frequency is 162.5MHz for China ADS, which consists of superconducting cavity amplitude stability control, phase stability control and the cavity resonance frequency control. The LLRF control system is based on four samples IQ quadrature demodulation technique consisting an all-digital closed-loop feedback control. This paper completed the first generation of ADS LLRF control system in the low-temperature superconducting cavities LLRF stability and performance online tests. Through testing, to verify the performance of LLRF control system, to analysis on emerging issues, and in accordance with the experimental data, to summarize LLRF control system performance to accumulate experience for the future control of superconducting cavities.
Generation of nonclassical states in a large detuning cavity
Zhang Ying-Jie; Ren Ting-Qi; Xia Yun-Jie
2008-01-01
By using the theory of cavity QED, we study the system in which a two-level atom interacts with a cavity in the case of large detuning. Through the selective detecting of atomic state, SchrSdinger cat states and entangled coherent states are easily generated. When the atom is driven by a weak classical field and the cavity field is in the Schr(o)dinger cat state, we study the conditions of generating the Fock states and the maximal success probability. The maximal success probability in our scheme is larger than the previous one.
Environment-Assisted Speed-up of the Field Evolution in Cavity Quantum Electrodynamics
We measure the quantum speed of the state evolution of the field in a weakly-driven optical cavity QED system. To this end, the mode of the electromagnetic field is considered as a quantum system of interest with a preferential coupling to a tunable environment: the atoms. By controlling the environment, i.e., changing the number of atoms coupled to the optical cavity mode, an environment assisted speed-up is realized: the quantum speed of the state re-population in the optical cavity increases with the coupling strength between the optical cavity mode and this non-Markovian environment (the number of atoms)
Dynamical mass generation in QED3
We study chiral symmetry breaking for QED[3] with N fermion flavours, just above the critical threshold. By analysis of a consistently truncated Schwinger-Dyson system for the fermion propagator and the fermion-boson vertex, we argue that the critical coupling must be strictly positive. (author). 19 refs.; 5 figs.; 3 tabs
Proposal for a loophole-free Bell test based on spin-photon interactions in cavities
Brunner, Nicolas; Young, Andrew B.; Hu, Chengyong; Rarity, John G.
2013-01-01
We present a scheme to demonstrate loophole-free Bell inequality violation where the entanglement between photon pairs is transferred to solid state (spin) qubits mediated by cavity QED interactions. As this transfer can be achieved in a heralded way, our scheme is basically insensitive to losses on the channel, and works also in the weak coupling regime. We consider potential experimental realizations using single atom, colour centre and quantum dot cavity systems. Finally our scheme appears...
Indirect Coupling between Two Cavity Photon Systems via Ferromagnetic Resonance
Hyde, Paul; Harder, Michael; Match, Christophe; Hu, Can-Ming
2016-01-01
We experimentally realize indirect coupling between two cavity modes via strong coupling with the ferromagnetic resonance in Yttrium Iron Garnet (YIG). We find that some indirectly coupled modes of our system can have a higher microwave transmission than the individual uncoupled modes. Using a coupled harmonic oscillator model, the influence of the oscillation phase difference between the two cavity modes on the nature of the indirect coupling is revealed. These indirectly coupled microwave modes can be controlled using an external magnetic field or by tuning the cavity height. This work has potential for use in controllable optical devices and information processing technologies.
Triple optomechanical induced transparency in a two-cavity system
Shi-Chao, Wu; Li-Guo, Qin; Jun, Jing; Guo-Hong, Yang; Zhong-Yang, Wang
2016-05-01
We theoretically investigate the optomechanical induced transparency (OMIT) phenomenon in a two-cavity system which is composed of two optomechanical cavities. Both of the cavities consist of a fixed mirror and a high-Q mechanical resonator, and they couple to each other via a common waveguide. We show that in the presence of a strong pump field applied to one cavity and a weak probe field applied to the other, a triple-OMIT can be observed in the output field at the probe frequency. The two mechanical resonators in the two cavities are identical, but they lead to different quantum interference pathways. The transparency windows are induced by the coupling of the two cavities and the optical pressure radiated to the mechanical resonators, which can be controlled via the power of the pump field and the coupling strength of the two cavities. Project supported by the Strategic Priority Research Program, China (Grant No. XDB01010200), the Hundred Talents Program of the Chinese Academy of Sciences (Grant No. Y321311401), and the National Natural Sciences Foundation of China (Grant Nos. 11347147 and 1547035).
Jasmin C. Blanchette
2016-01-01
Full Text Available This paper surveys the emerging methods to automate reasoning over large libraries developed with formal proof assistants. We call these methods hammers. They give the authors of formal proofs a strong "one-stroke" tool for discharging difficult lemmas without the need for careful and detailed manual programming of proof search.The main ingredients underlying this approach are efficient automatic theorem provers that can cope with hundreds of axioms, suitable translations of richer logics to their formalisms, heuristic and learning methods that select relevant facts from large libraries, and methods that reconstruct the automatically found proofs inside the proof assistants.We outline the history of these methods, explain the main issues and techniques, and show their strength on several large benchmarks. We also discuss the relation of this technology to the QED Manifesto and consider its implications for QED-style efforts.
Generation of entanglement in cavity QED
Montenegro, V.; Orszag, M.
2011-01-01
Presentamos un modelo para generar entrelazamiento con atomos localizados en cavidades distantes. Consiste en dos cavidades conectadas ́ ́ por una fibra optica, donde cada cavidad interactua con un solo atomo de dos niveles. Para ciertos valores de los par ́ metros de acoplamiento a ́ ́ atomo–cavidad y cavidad–fibra, encontramos un plateau amplio en el tiempo para la concurrencia entre los atomos. El aumento del ́ desentonamiento atomo-cavidad da lugar a un aumento l ́neal en el ancho de...
Integrated optics for coupled-cavity QED
Lepert, G.; Hinds, E. A. [Centre for Cold Matter, Imperial College London (United Kingdom)
2014-12-04
We present an array of Fabry-Pérot free space microcavities, intended to contain atoms or other quantum emitters, coupled to each other by waveguides resonators on a chip. The concept is highly scalable and offers a unique degree of control, making it a promising platform for quantum simulations. We demonstrate experimentally the basic units of the device.
Quantum Mechanical Description of Raman Scattering from Molecules in Plasmonic Cavities.
Schmidt, Mikolaj K; Esteban, Ruben; González-Tudela, Alejandro; Giedke, Geza; Aizpurua, Javier
2016-06-28
Plasmon-enhanced Raman scattering can push single-molecule vibrational spectroscopy beyond a regime addressable by classical electrodynamics. We employ a quantum electrodynamics (QED) description of the coherent interaction of plasmons and molecular vibrations that reveal the emergence of nonlinearities in the inelastic response of the system. For realistic situations, we predict the onset of phonon-stimulated Raman scattering and a counterintuitive dependence of the anti-Stokes emission on the frequency of excitation. We further show that this QED framework opens a venue to analyze the correlations of photons emitted from a plasmonic cavity. PMID:27203727
Fermilab linac upgrade side coupled cavity temperature control system
Each cavity section has a temperature control system which maintains the resonant frequency by exploiting the 17.8 ppm/degree C frequency sensitivity of the copper cavities. Each accelerating cell has a cooling tube brazed azimuthally to the outside surface. Alternate supply and return connection to the water manifolds reduce temperature gradients and maintain physical alignment of the cavity string. Special tubing with spiral inner fins and large flow rate are used to reduce the film coefficient. Temperature is controlled by mixing chilled water with the water circulating between the cavity and the cooling skid located outside the radiation enclosure. Chilled water flow is regulated with a valve controlled by a local microcomputer. The temperature loop set point will be obtained from a slower loop which corrects the phase error between the cavity section and the rf drive during normal beam loaded conditions. Time constants associated with thermal gradients induced in the cavity with the rf power require programming it to the nominal 7.1 MW level over a 1 minute interval to limit the reverse power. 4 refs., 4 figs
Fermilab linac upgrade side coupled cavity temperature control system
Each cavity section has a temperature control system which maintains the resonant frequency by exploiting the 17.8 ppm/C frequency sensitivity of the copper cavities. Each accelerating cell has a cooling tube brazed azimuthally to the outside surface. Alternate supply and return connection to the water manifolds reduce temperature gradients and maintain physical alignment of the cavity string. Special tubing with a spiral inner fins and a large flow rate are used to reduce the film coefficient. Temperature is controlled by mixing chilled water with the water circulating between the cavity and the cooling skid located outside the radiation enclosure. Chilled water flow is regulated with a valve controlled by a local micro computer. The temperature loop set point will be obtained from a slower loop which corrects the phase error between the cavity section and the rf drive during normal beam loaded conditions. Time constants associated with thermal gradients induced in the cavity with the rf power require programming it to the nominal 7.1 MW level over a 1 minute interval to limit the reverse power
A geometric approach to identify cavities in particle systems
Voyiatzis, Evangelos; Böhm, Michael C.; Müller-Plathe, Florian
2015-11-01
The implementation of a geometric algorithm to identify cavities in particle systems in an open-source python program is presented. The algorithm makes use of the Delaunay space tessellation. The present python software is based on platform-independent tools, leading to a portable program. Its successful execution provides information concerning the accessible volume fraction of the system, the size and shape of the cavities and the group of atoms forming each of them. The program can be easily incorporated into the LAMMPS software. An advantage of the present algorithm is that no a priori assumption on the cavity shape has to be made. As an example, the cavity size and shape distributions in a polyethylene melt system are presented for three spherical probe particles. This paper serves also as an introductory manual to the script. It summarizes the algorithm, its implementation, the required user-defined parameters as well as the format of the input and output files. Additionally, we demonstrate possible applications of our approach and compare its capability with the ones of well documented cavity size estimators.
QED Reloaded: Towards a Pluralistic Formal Library of Mathematical Knowledge
Michael Kohlhase; Florian Rabe
2016-01-01
Proposed in 1994, the ``QED project'' was one of the seminally influential initiatives in automated reasoning: It envisioned the formalization of ``all of mathematics'' and the assembly of these formalizations in a single coherent database. Even though it never led to the concrete system, communal resource, or even joint research envisioned in the QED manifesto, the idea lives on and shapes the research agendas of a significant part of the communityThis paper surveys a decade of work on repre...
A coupled microwave-cavity system in the Rydberg-atom cavity detector for dark matter axions
Tada, M; Shibata, M; Kominato, K; Ogawa, I; Funahashi, H; Yamamoto, K; Matsuki, S
2001-01-01
A coupled microwave-cavity system of cylindrical TM$_{010}$ single-mode has been developed to search for dark matter axions around 10 $\\mu {\\rm eV}$(2.4 GHz) with the Rydberg-atom cavity detector at 10 mK range temperature. One component of the coupled cavity (conversion cavity) made of oxygen-free high-conductivity copper is used to convert an axion into a single photon with the Primakoff process in the strong magnetic field, while the other component (detection cavity) made of Nb is utilized to detect the converted photons with Rydberg atoms passed through it without magnetic field. Top of the detection cavity is attached to the bottom flange of the mixing chamber of a dilution refrigerator, thus the whole cavity is cooled down to 10 mK range to reduce the background thermal blackbody-photons in the cavity. The cavity resonant frequency is tunable over $\\sim$ 15% by moving dielectric rods inserted independently into each part of the cavities along the cylindrical axis. In order to reduce the heat load from ...
Strong atom-field coupling for Bose-Einstein condensates in an optical cavity on a chip
Colombe, Yves; Steinmetz, Tilo; Dubois, Guilhem; Linke, Felix; Hunger, David; REICHEL, Jakob
2007-01-01
An optical cavity enhances the interaction between atoms and light, and the rate of coherent atom-photon coupling can be made larger than all decoherence rates of the system. For single atoms, this strong coupling regime of cavity quantum electrodynamics (cQED) has been the subject of spectacular experimental advances, and great efforts have been made to control the coupling rate by trapping and cooling the atom towards the motional ground state, which has been achieved in one dimension so fa...
Chester, Shai M
2016-01-01
We initiate the conformal bootstrap study of Quantum Electrodynamics in $2+1$ space-time dimensions (QED$_{3}$) with $N$ flavors of charged fermions by focusing on the 4-point function of four monopole operators with the lowest unit of topological charge. We obtain upper bounds on the scaling dimension of the doubly-charged monopole operator, with and without assuming other gaps in the operator spectrum. Intriguingly, we find a (gap-dependent) kink in these bounds that comes reasonably close to the large $N$ extrapolation of the scaling dimensions of the singly-charged and doubly-charged monopole operators down to $N=4$ and $N=6$.
Autonomous quantum thermal machines in atom-cavity systems
Mitchison, Mark T; Prior, Javier; Woods, Mischa P; Plenio, Martin B
2016-01-01
An autonomous quantum thermal machine comprising a trapped atom or ion placed inside an optical cavity is proposed and analysed. Such a machine can operate as a heat engine whose working medium is the quantised atomic motion, or as an absorption refrigerator which cools without any work input. Focusing on the refrigerator mode, we predict that it is possible with state-of-the-art technology to cool a trapped ion almost to its motional ground state using a thermal light source such as sunlight. We nonetheless find that a laser or similar reference system is necessary to stabilise the cavity frequencies. Furthermore, we establish a direct and heretofore unacknowledged connection between the abstract theory of quantum absorption refrigerators and practical sideband cooling techniques. We also highlight and clarify some assumptions underlying several recent theoretical studies on self-contained quantum engines and refrigerators. Our work indicates that cavity quantum electrodynamics is a promising and versatile e...
Observation of Non-Markovian Dynamics of a Single Quantum Dot in a Micropillar Cavity
Madsen, Kristian Høeg; Ates, Serkan; Lund-Hansen, Toke; Löffler, A.; Reitzenstein, S.; Forchel, A.; Lodahl, Peter
2011-01-01
We measure the detuning-dependent dynamics of a quasiresonantly excited single quantum dot coupled to a micropillar cavity. The system is modeled with the dissipative Jaynes-Cummings model where all experimental parameters are determined by explicit measurements. We observe non-Markovian dynamics...... when the quantum dot is tuned into resonance with the cavity leading to a nonexponential decay in time. Excellent agreement between experiment and theory is observed with no free parameters providing the first quantitative description of an all-solid-state cavity QED system based on quantum dot...
Solid state high power RF system for superconducting cavities
Solid State High Power RF System is proposed for XFEL and ILC. It includes individual RF power supply for each SC cavity and common control system. Each RF power supply includes Solid State Generator, circulator and Q-tuner. Triggering, synchronization, output power and phase of each Solid State Generator are controlled from the common control system through fiber-optic lines. Main parameters of Solid State Generator are: frequency 1.3 GHz, peak power 128 kW, pulse length 1.4 msec, repetition rate 10 Hz, average power 1.8 kW, CW power 2.5 kW. Advantages of Solid State High Power RF System are: simple triggering, synchronization, output power and phase adjustment for all cavities separately, operation both in pulse and in CW modes, unlimited lifetime, no high voltage, no oil-tank, compactness.
Hwang, Myung-Joong; Kim, M S; Choi, Mahn-Soo
2016-04-15
We explore the photon population dynamics in two coupled circuit QED systems. For a sufficiently weak intercavity photon hopping, as the photon-cavity coupling increases, the dynamics undergoes double transitions first from a delocalized to a localized phase and then from the localized to another delocalized phase. The latter delocalized phase is distinguished from the former one; instead of oscillating between the two cavities, the photons rapidly quasiequilibrate over the two cavities. These intriguing features are attributed to an interplay between two qualitatively distinctive nonlinear behaviors of the circuit QED systems in the utrastrong coupling regime, whose distinction has been widely overlooked. PMID:27127967
Physical Angular Momentum Separation for QED
Sun, Weimin
2016-01-01
We study the non-uniqueness problem of the gauge-invariant angular momentum separation for the case of QED, which stems from the recent controversy concerning the proper definitions of the orbital angular momentum and spin operator of the individual parts of a gauge field system. For the free quantum electrodynamics without matter, we show that the basic requirement of Euclidean symmetry selects a unique physical angular momentum separation scheme from the multitude of the possible angular momentum separation schemes constructed using the various Gauge Invariant Extentions. Based on these results, we propose a set of natural angular momentum separation schemes for the case of interacting QED by invoking the formalism of asymptotic fields. Some perspectives on such a problem for the case of QCD are briefly discussed.
Design of a high power three-cavity gyroklystron system
The University of Maryland is designing a 30 MW gyroklystron amplifier to demonstrate the feasibility of this type of device as a driver for future 1-TeV linear colliders. The authors' system uses a beam produced by a magnetron injection gun. The system is designed to yield a 500 kV, 200 A, 1 μs beam with α = 1.5 and low velocity spread. Linear collider systems require a large number of microwave sources operating in a phase-locked mode, and thus large input powers will not be available. The authors' modeling has shown that to achieve the necessary gain they must use a system with three or more cavities. The experimental effort has focused on characterizing the beam with air core transformers, 90 degrees-sector capacitive probes, diamagnetic loops and a B probe. The authors have also built and have tested a TE011 two-cavity device. This has allowed to study the start oscillation current and test the design codes on a relatively simple system before attempting the more complex three-cavity system
Cooling and control of a cavity opto-electromechanical system
Lee, Kwan H; Harris, Glen I; Knittel, Joachim; Bowen, Warwick P
2009-01-01
Mechanical oscillators provide a quintessential example of the profound difference between quantum and classical behaviour. However, the quantum regime is yet to be observed. Rapid progress is underway in cavity optomechanical systems (COMS) and nanoelectromechanical systems (NEMS). COMS have superior mechanical transduction sensitivity, able to resolve mechanical zero-point fluctuations. However, the electrical actuation of NEMS provides far greater scope for quantum control. By combining electrical gradient forces from NEMS with the ultrasensitive transduction from COMS, we implement a cavity optoelectromechanical system (COEMS), demonstrating both control and feedback cooling capabilities. Out-of-loop mechanical transduction provides, for the first time, independent temperature verification even when opto-mechanical correlations exist due to strong interactions such as measurement backaction. This technology has significance in fundamental science, improving our capacity to engineer mechanical quantum syst...
The thermodynamics of gauge theories such as QED and QCD are slightly more complicated than that of theories such as scalar field theory or free fremion field theory. We shall consider QED in some detail in this lecture, and shall generalize the results we find to more complicated gauge theories such as QCD. The results of this analysis are easily generalized to non-abelian gauge theories with scalar fields and spontaneous symmetry breaking such as GUTS
Cavity Beam Position Monitor System for ATF2
Boogert, Stewart; /Oxford U., JAI; Boorman, Gary; /Oxford U., JAI; Swinson, Christina; /Oxford U., JAI; Ainsworth, Robert; /Royal Holloway, U. of London; Molloy, Stephen; /Royal Holloway, U. of London; Aryshev, Alexander; /KEK, Tsukuba; Honda, Yosuke; /KEK, Tsukuba; Tauchi, Toshiaki; /KEK, Tsukuba; Terunuma, Nobuhiro; /KEK, Tsukuba; Urakawa, Junji; /KEK, Tsukuba; Frisch, Josef; /SLAC; May, Justin; /SLAC; McCormick, Douglas; /SLAC; Nelson, Janice; /SLAC; Smith, Tonee; /SLAC; White, Glen; /SLAC; Woodley, Mark; /SLAC; Heo, Ae-young; /Kyungpook Natl. U.; Kim, Eun-San; /Kyungpook Natl. U.; Kim, Hyoung-Suk; /Kyungpook Natl. U.; Kim, Youngim; /Kyungpook Natl. U. /University Coll. London /Kyungpook Natl. U. /Fermilab /Pohang Accelerator Lab.
2012-07-09
The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a future high energy lepton linear collider. The ATF2 beam-line is instrumented with a total of 38 C and S band resonant cavity beam position monitors (CBPM) with associated mixer electronics and digitizers. The current status of the BPM system is described, with a focus on operational techniques and performance. The ATF2 C-band system is performing well, with individual CBPM resolution approaching or at the design resolution of 50 nm. The changes in the CBPM calibration observed over three weeks can probably be attributed to thermal effects on the mixer electronics systems. The CW calibration tone power will be upgraded to monitor changes in the electronics gain and phase. The four S-band CBPMs are still to be investigated, the main problem associated with these cavities is a large cross coupling between the x and y ports. This combined with the large design dispersion in that degion makes the digital signal processing difficult, although various techniques exist to determine the cavity parameters and use these coupled signals for beam position determination.
Lange, B.
2006-12-20
Combining an optical resonator with an ion trap provides the possibility for QED experiments with single or few particles interacting with a single mode of the electro-magnetic field (Cavity-QED). In the present setup, fluctuations in the count rate on a time scale below 30 seconds were purely determined by the photon statistics due to finite emission and detection efficiency, whereas a marginal drift of the system was noticeable above 200 seconds. To find methods to increase the efficiency of the photon source, investigations were conducted and experimental improvements of the setup implemented in the frame of this thesis. Damping of the resonator field and coupling of ion and field were considered as the most important factors. To reduce the damping of the resonator field, a resonator with a smaller transmissivity of the output mirror was set up. The linear trap used in the experiment allows for the interaction of multiple ions with the resonator field, so that more than one photon may be emitted per pump pulse. This was investigated in this thesis with two ions coupled to the resonator. The cross correlation of the emitted photons was measured with the Hanbury Brown-Twiss method. (orig.)
Axisymmetric Predictions of Fluid Flow inside a Rotating Cavity System
Mujeebuddin Memon
2013-07-01
Full Text Available Accurate prediction of fluid flow in the rotating cavity system is of practical interest as it is most commonly used in the gas turbine engines and compressors. This paper presents the numerical predictions of a rotating cavity flow system for Reynolds numbers of the range 1x105 < Re? < 4x105 and two different mass flow rates Cw=1092 and 2184. A finite-difference technique is employed for a Steady-state solution in the axisymmetric cylindrical polar coordinate frame of reference. The two low Reynolds number turbulence models, the low Reynolds number k-? model and the low Reynolds number second moment closure have been used to compute the basic characteristics of the flow inside the rotating cavity flow system. Different flow regions have been identified by computing flow structures and dimensions of those regions have also been studied under different flow rates. A comparison of the computed variation of moment coefficient of both the turbulence models are presented for the above mentioned parameters and the parametric effects on the moment coefficients have been discussed
The generation and control of quantum states of spatially-separated qubits distributed in different cavities constitute fundamental tasks in cavity quantum electrodynamics (QED). An interesting question in this context is how to prepare entanglement and realize quantum information transfer between qubits located at different cavities, which are important in large-scale quantum information processing. In this paper, we consider a physical system consisting of two cavities and three qubits. Two of the qubits are placed in two different cavities while the remaining one acts as a coupler, which is used to connect the two cavities. We propose an approach for generating quantum entanglement and implementing quantum information transfer between the two spatially-separated inter-cavity qubits. The quantum operations involved in this proposal are performed by a virtual photon process; thus the cavity decay is greatly suppressed during operations. In addition, to complete these tasks, only one coupler qubit and one operation step are needed. Moreover, there is no need to apply classical pulses, so that the engineering complexity is much reduced and the operation procedure is greatly simplified. Finally, our numerical results illustrate that high-fidelity implementation of this proposal using superconducting phase qubits and one-dimensional transmission line resonators is feasible for current circuit QED implementations. This proposal can also be applied to other types of superconducting qubits, including flux and charge qubits. (paper)
Yang, Chui-Ping; Su, Qi-Ping; Nori, Franco
2013-11-01
The generation and control of quantum states of spatially-separated qubits distributed in different cavities constitute fundamental tasks in cavity quantum electrodynamics (QED). An interesting question in this context is how to prepare entanglement and realize quantum information transfer between qubits located at different cavities, which are important in large-scale quantum information processing. In this paper, we consider a physical system consisting of two cavities and three qubits. Two of the qubits are placed in two different cavities while the remaining one acts as a coupler, which is used to connect the two cavities. We propose an approach for generating quantum entanglement and implementing quantum information transfer between the two spatially-separated inter-cavity qubits. The quantum operations involved in this proposal are performed by a virtual photon process; thus the cavity decay is greatly suppressed during operations. In addition, to complete these tasks, only one coupler qubit and one operation step are needed. Moreover, there is no need to apply classical pulses, so that the engineering complexity is much reduced and the operation procedure is greatly simplified. Finally, our numerical results illustrate that high-fidelity implementation of this proposal using superconducting phase qubits and one-dimensional transmission line resonators is feasible for current circuit QED implementations. This proposal can also be applied to other types of superconducting qubits, including flux and charge qubits.
Entangling atoms in bad cavities
Sorensen, Anders S.; Molmer, Klaus
2002-01-01
We propose a method to produce entangled spin squeezed states of a large number of atoms inside an optical cavity. By illuminating the atoms with bichromatic light, the coupling to the cavity induces pairwise exchange of excitations which entangles the atoms. Unlike most proposals for entangling atoms by cavity QED, our proposal does not require the strong coupling regime g^2/\\kappa\\Gamma>> 1, where g is the atom cavity coupling strength, \\kappa is the cavity decay rate, and \\Gamma is the dec...
Existence of a strong coupling phase in QED has been suggested in solutions of the Schwinger-Dyson equation and in Monte Carlo simulation of lattice QED. In this article we recapitulate the previous arguments, and formulate the problem in the modern framework of the renormalization theory, Wilsonian renormalization. This scheme of renormalization gives the best understanding of the basic structure of a field theory especially when it has a multi-phase structure. We resolve some misleading arguments in the previous literature. Then we set up a strategy to attack the strong phase, if any. We describe a trial; a coupled Schwinger-Dyson equation. Possible picture of the strong coupling phase QED is presented. (author)
Squeezing enhancement by damping in a driven atom-cavity system
Nha, H; Kim, S W; An, K; Nha, Hyunchul; Chough, Young-Tak; Kim, Sang Wook; An, Kyungwon
2001-01-01
In a driven atom-cavity coupled system in which the two-level atom is driven by a classical field, the cavity mode which should be in a coherent state in the absence of its reservoir, can be squeezed by coupling to its reservoir. The squeezing effect is enhanced as the damping rate of the cavity is increased to some extent.
QED Reloaded: Towards a Pluralistic Formal Library of Mathematical Knowledge
Michael Kohlhase
2016-01-01
Full Text Available Proposed in 1994, the ``QED project'' was one of the seminally influential initiatives in automated reasoning: It envisioned the formalization of ``all of mathematics'' and the assembly of these formalizations in a single coherent database. Even though it never led to the concrete system, communal resource, or even joint research envisioned in the QED manifesto, the idea lives on and shapes the research agendas of a significant part of the communityThis paper surveys a decade of work on representation languages and knowledge management tools for mathematical knowledge conducted in the KWARC research group at Jacobs University Bremen.It assembles the various research strands into a coherent agenda for realizing the QED dream with modern insights and technologies.
Universal quantum gates for photon-atom hybrid systems assisted by bad cavities
Wang, Guan-yu; Liu, Qian; Wei, Hai-Rui; Ai, Qing; Deng, Fu-Guo
2015-01-01
We present two deterministic schemes for constructing a CNOT gate and a Toffoli gate on photon-atom and photon-atom-atom hybrid quantum systems assisted by bad cavities, respectively. They are achieved by cavity-assisted photon scattering and work in the intermediate coupling region with bad cavities, which relaxes the difficulty of their implementation in experiment. Also, bad cavities are feasible for fast quantum operations and reading out information. Compared with previous works, our sch...
Universal quantum gates for photon-atom hybrid systems assisted by bad cavities
Guan-Yu Wang; Qian Liu; Hai-Rui Wei; Tao Li; Qing Ai; Fu-Guo Deng
2016-01-01
We present two deterministic schemes for constructing a CNOT gate and a Toffoli gate on photon-atom and photon-atom-atom hybrid quantum systems assisted by bad cavities, respectively. They are achieved by cavity-assisted photon scattering and work in the intermediate coupling region with bad cavities, which relaxes the difficulty of their implementation in experiment. Also, bad cavities are feasible for fast quantum operations and reading out information. Compared with previous works, our sch...
Leading quantum gravitational corrections to QED
Butt, M. S.
2006-01-01
We consider the leading post-Newtonian and quantum corrections to the non-relativistic scattering amplitude of charged spin-1/2 fermions in the combined theory of general relativity and QED. The coupled Dirac-Einstein system is treated as an effective field theory. This allows for a consistent quantization of the gravitational field. The appropriate vertex rules are extracted from the action, and the non-analytic contributions to the 1-loop scattering matrix are calculated in the non-relativi...
CFD modeling of the HTR reactor cavity cooling system
This report describes the heat transport under accident conditions from the reactor vessel wall of the INCOGEN installation to the environment. For this purpose, the heat transfer mechanisms as well as the flow patterns inside the cavity and the Reactor Cavity Cooling System (RCCS) have been calculated by the CFD (Computational Fluid Dynamics) code called CFDS-FLOW3D. The main purpose of the calculations is to determine the vessel wall temperature at which the power produced in the vessel is removed. An important assumption of the calculations is that a total of 1 MW of decay power and fission power has to be removed by the RCCS under accident conditions. In the reference calculation, about 80% of the heat is transported by radiation to the RCCS, while the remaining 20% is transported by convection of the gas in the cavity. The maximum calculated temperature on the outside of the vessel in 634 K. The reference calculation is assessed by a number of sensitivity calculations. In these calculations, the influence of the following parameters on the reactor vessel wall temperature has been determined: The turbulence model, the properties of the inlet and the outlet structures, the heat loss from the reactor vessel wall, the emissivity of structures, and the interaction between gas and radiation. Most of the parameters investigated have a small influence on the reactor vessel wall temperature. The following changes result in an increase of the reactor vessel wall temperature by 25 K or more: An increase of the heat loss from 1 MW to 2 MW, an increase of the inlet temperature from 300 K to 350 K, a decrease of the emissivity of the reactor vessel wall from 0.8 to 0.6, or very high concentrations of scattering aerosol particles. (orig.)
TESLA cavity modeling and digital implementation in FPGA technology for control system development
Czarski, T.; Pozniak, K.T.; Romaniuk, R.S. [Warsaw Univ. of Technology (Poland); Simrock, S. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2006-07-01
The electromechanical model of the TESLA cavity has been implemented in FPGA technology for real-time testing of the control system. The model includes Lorentz force detuning and beam loading effects. Step operation and vector stimulus operation modes are applied for the evaluation of a FPGA cavity simulator operated by a digital controller. The performance of the cavity hardware model is verified by comparing with a software model of the cavity implemented in the MATLAB system. The numerical aspects are considered for an optimal DSP calculation. Some experimental results are presented for different cavity operational conditions. (orig.)
TESLA cavity modeling and digital implementation in FPGA technology for control system development
The electromechanical model of the TESLA cavity has been implemented in FPGA technology for real-time testing of the control system. The model includes Lorentz force detuning and beam loading effects. Step operation and vector stimulus operation modes are applied for the evaluation of a FPGA cavity simulator operated by a digital controller. The performance of the cavity hardware model is verified by comparing with a software model of the cavity implemented in the MATLAB system. The numerical aspects are considered for an optimal DSP calculation. Some experimental results are presented for different cavity operational conditions. (orig.)
QED corrections to atomic wavefunctions in highly charged ions
Bound electron states in highly charged ions are strongly influenced by the effects of relativity and quantum electrodynamics (QED). These effects induce shifts of the binding energies as well as corrections to observables related to atomic processes. In this work a numerical procedure is described and implemented in which the QED effects are treated as corrections to relativistic bound-state wavefunctions. This approach, which is based on the recently developed covariant evolution-operator formalism, allows for a merging of QED with the standard methods of many-body perturbation theory. In particular, it enables an evaluation of the combined effect of QED and electron correlation in few-electron systems. Numerical results for this effect are presented for the ground state energy of helium-like ions. A detailed analysis of the contribution from the electron self-energy is carried out in both the Feynman and Coulomb gauge. It is found that the Feynman gauge suffers from large numerical cancellations and acquires significant contributions from terms involving multiple interactions with the nuclear potential (the so-called many-potential terms), while the Coulomb gauge is well suited for an approximate treatment based on terms involving only freely propagating electrons (the zero-potential terms). With the help of QED-corrected wavefunctions it is also possible to compute corrections to observables in basic atomic processes. In this work some of the one-loop QED corrections (those derivable from perturbed wavefunctions and energies) to the differential cross section and distribution of polarization in radiative recombination of initially bare uranium nuclei are evaluated, as well as the corresponding corrections to the ratio τE1/τM2 of the electric dipole and magnetic quadrupole transition amplitudes in the 2p3/2→1s radiative decay of hydrogenlike uranium. The results from these calculations are all of the expected magnitude, namely on the order of the fine
QED corrections to atomic wavefunctions in highly charged ions
Holmberg, Johan
2015-11-18
Bound electron states in highly charged ions are strongly influenced by the effects of relativity and quantum electrodynamics (QED). These effects induce shifts of the binding energies as well as corrections to observables related to atomic processes. In this work a numerical procedure is described and implemented in which the QED effects are treated as corrections to relativistic bound-state wavefunctions. This approach, which is based on the recently developed covariant evolution-operator formalism, allows for a merging of QED with the standard methods of many-body perturbation theory. In particular, it enables an evaluation of the combined effect of QED and electron correlation in few-electron systems. Numerical results for this effect are presented for the ground state energy of helium-like ions. A detailed analysis of the contribution from the electron self-energy is carried out in both the Feynman and Coulomb gauge. It is found that the Feynman gauge suffers from large numerical cancellations and acquires significant contributions from terms involving multiple interactions with the nuclear potential (the so-called many-potential terms), while the Coulomb gauge is well suited for an approximate treatment based on terms involving only freely propagating electrons (the zero-potential terms). With the help of QED-corrected wavefunctions it is also possible to compute corrections to observables in basic atomic processes. In this work some of the one-loop QED corrections (those derivable from perturbed wavefunctions and energies) to the differential cross section and distribution of polarization in radiative recombination of initially bare uranium nuclei are evaluated, as well as the corresponding corrections to the ratio τ{sub E1}/τ{sub M2} of the electric dipole and magnetic quadrupole transition amplitudes in the 2p{sub 3/2}→1s radiative decay of hydrogenlike uranium. The results from these calculations are all of the expected magnitude, namely on the order
Dissipated power measurements in the A0 SRF cavity system
Fermilab operates a single TESLA 9-cell superconducting RF cavity in support of a photoelectron R and D beam line. Power going into the 1.8K cryogenic system via static heat leak and RF dissipation is measured from the rate of rise of the pressure in the helium bath. This paper describes the techniques used to determine the cryostat heat load and the RF performance of the cavity. A photo-injector has been constructed at Fermilab to produce a low-energy (14--18 MeV) electron beam with high charge per bunch (8 nC), short bunch length (1 mm RMS), and small transverse emittance (<20 mm mrad). The facility was used to commission a photo-cathode RF gun for the TESLA Test Facility (TTF) Linac at DESY. At present, the Fermilab machine is being used for R and D in bunch length compression and fast beam diagnostics; experiments in plasma wake field acceleration and channeling acceleration are in preparation
Ooi, K. J. A.; Bai, P.; Gu, M. X.; Ang, L. K.
2012-07-01
A plasmonic coupled-cavity system, which consists of a quarter-wave coupler cavity, a resonant Fabry-Pérot detector nanocavity, and an off-resonant reflector cavity, is used to enhance the localization of surface plasmons in a plasmonic detector. The coupler cavity is designed based on transmission line theory and wavelength scaling rules in the optical regime, while the reflector cavity is derived from off-resonant resonator structures to attenuate transmission of plasmonic waves. We observed strong coupling of the cavities in simulation results, with an 86% improvement of surface plasmon localization achieved. The plasmonic coupled-cavity system may find useful applications in areas of nanoscale photodetectors, sensors, and an assortment of plasmonic-circuit devices.
The Phase Servo Tuner Control system of the ALS 500 MHz cavity
Three 500 MHz cavities are used in the Booster and Storage Ring of the Advanced Light Source (ALS). Due to different varying parameters, a control system is required to keep the cavities in tune during operation. The tuning of the 500 MHz cavity is achieved by detecting the phase error between the drive signal and the cavity probe signal. The error signal is amplified and used to drive a stepping motor which in turn moves a metallic cylinder in or out of the cavity to achieve tuning
Note: auto-relock system for a bow-tie cavity for second harmonic generation.
Haze, Shinsuke; Hata, Sousuke; Fujinaga, Munekazu; Mukaiyama, Takashi
2013-02-01
This Note reports on the implementation of an automatic relocking system for a bow-tie cavity for second harmonic generation to produce an ultra-violet laser source. The system is based on a sample-and-hold technique for controlling the cavity length using simple servo electronics. Long-term stabilization of the cavity output power is successfully achieved, which makes this system suitable for designing stable atomic physics experiments. PMID:23464273
Cavity BPM System Tests for the ILC Spectrometer
Slater, M.
2007-12-21
The main physics program of the International Linear Collider (ILC) requires a measurement of the beam energy at the interaction point with an accuracy of 10{sup -4} or better. To achieve this goal a magnetic spectrometer using high resolution beam position monitors (BPMs) has been proposed. This paper reports on the cavity BPM system that was deployed to test this proposal. We demonstrate sub-micron resolution and micron level stability over 20 hours for a 1 m long BPM triplet. We find micron-level stability over 1 hour for 3 BPM stations distributed over a 30 m long baseline. The understanding of the behavior and response of the BPMs gained from this work has allowed full spectrometer tests to be carried out.
RF and Data Acquisition Systems for Fermilab's ILC SRF Cavity Vertical Test Stand
Fermilab is developing a facility for vertical testing of SRF cavities as part of a program to improve cavity performance reproducibility for the ILC. The RF system for this facility, using the classic combination of oscillator, phase detector/mixer, and loop amplifier to detect the resonant cavity frequency and lock onto the cavity, is based on the proven production cavity test systems used at Jefferson Lab for CEBAF and SNS cavity testing. The design approach is modular in nature, using commercial-off-the-shelf (COTS) components. This yields a system that can be easily debugged and modified, and with ready availability of spares. Data acquisition and control is provided by a PXI-based hardware platform in conjunction with software developed in the LabView programming environment. This software provides for amplitude and phase adjustment of incident RF power, and measures all relevant cavity power levels, cavity thermal environment parameters, as well as field emission-produced radiation. It also calculates the various cavity performance parameters and their associated errors. Performance during system commissioning and initial cavity tests will be presented
Updating of Optical Inspection System for 6 GHz Superconducting Cavities
YU; Guo-long
2013-01-01
As a validation tool for the material properties and the surface treatment process,6 GHz superconducting cavity needs complex surface treatment process during its manufacture.It is verynecessary to record and monitor the statues of the internal surface of the cavity after each surface treatment,such as ultrasonic washing,mechanical polishing,electronic polishing(EP),buffered chemical
Phonon routing in integrated optomechanical cavity-waveguide systems
Fang, Kejie; Luan, Xingsheng; Painter, Oskar
2015-01-01
The mechanical properties of light have found widespread use in the manipulation of gas-phase atoms and ions, helping create new states of matter and realize complex quantum interactions. The field of cavity-optomechanics strives to scale this interaction to much larger, even human-sized mechanical objects. Going beyond the canonical Fabry-Perot cavity with a movable mirror, here we explore a new paradigm in which multiple cavity-optomechanical elements are wired together to form optomechanical circuits. Using a pair of optomechanical cavities coupled together via a phonon waveguide we demonstrate a tunable delay and filter for microwave-over-optical signal processing. In addition, we realize a tight-binding form of mechanical coupling between distant optomechanical cavities, leading to direct phonon exchange without dissipation in the waveguide. These measurements indicate the feasibility of phonon-routing based information processing in optomechanical crystal circuitry, and further, to the possibility of re...
Lin Xiu; Li Hong-Cai; Yang Rong-Can; Huang Zhi-Ping
2007-01-01
This paper proposes a scheme for realizing entanglement swapping in cavity QED. The scheme is based on the resonant interaction of a two-mode cavity field with a A-type three-level atom. In contrast with the previously proposed schemes, the present scheme is ascendant, since the fidelity is 1.0 and the joint measurement isn't needed. And the scheme is experimentally feasible based on the current cavity QED technique.
Physicists believe that the world is described in terms of gauge theories. A popular technique for investigating these theories is to discretize them onto a lattice and simulate numerically by a computer, yielding so-called lattice gauge theory. Such computations require at least 1014 floating-point operations, necessitating the use of advanced architecture supercomputers such as the Connection Machine. Currently the most important gauge theory to be solved is that describing the sub-nuclear world of high energy physics: quantum chromo-dynamics (QCD). The simplest example of a gauge theory is Quantum electro-dynamics (QED), the theory which describes the interaction of electrons and photons. Simulation of QCD requires computer software very similar to that for the simpler QED problem. The authors' current QED code achieves a computational rate of 1.6 million lattice site updates per second for a Monte Carlo algorithm, and 7.4 million site updates per second for a microcanonical algorithm. The estimate performance for a Monte Carlo QCD code is 200,000 site updates per second (or 5.6 Gflops/sec)
The relevance of Quantum Electrodynamics (Qed) in contemporary atomic structure theory is reviewed. Recent experimental advances allow both the production of heavy ions of high charge as well as the measurement of atomic properties with a precision never achieved before. The description of heavy atoms with few electrons via the successive incorporation of one, two, etcetera photons in a rigorous manner and within the bound state Furry representation of Qed is technically feasible. For many-electron atoms the many-body (correlation) effects are very important and it is practically impossible to evaluate all the relevant Feynman diagrams to the required accuracy. Thus, it is necessary to develop a theoretical scheme in which the radiative and nonradiative effects are taken into account in an effective way making emphasis in electronic correlation. Preserving gauge invariance, and avoiding both continuum dissolution and variational collapse are basic problems that must be solved when using effective potential methods and finite-basis representations of them. In this context, we shall discuss advances and problems in the description of atoms as Qed bound states. (Author)
Two-resonator circuit QED: A superconducting quantum switch
Coupling different kind of superconducting (sc) qubits to on-chip microwave resonators has strongly advanced the field of circuit QED. Regarding the application of circuit QED systems in quantum information processing it would be highly desirable to switch on and off the interaction between two resonators. We introduce a formalism for two-resonator circuit QED where two on-chip microwave resonators are simultaneously coupled to one sc qubit. In this three-circuit network, the qubit mediates a geometric and a dynamic second-order interaction between the two resonators. These two coupling strengths can be tuned to be equal by varying the qubit operation point, thus permitting to switch on and off the interaction between the resonators. We discuss the effect of the qubit on the dynamic second-order coupling and how it can be deliberately manipulated to realize a sc quantum switch. Finally, we present a realistic design for implementing a two-resonator circuit QED setup based on a flux qubit and show preliminary experimental results.
Zhong Zhi-Rong
2008-01-01
An alternative scheme to approximately conditionally teleport entangled two-mode cavity state without Bell state measurement in cavity QED is proposed.The scheme is based on the resonant interaction of a ladder-type three-level atom with two bimodal cavities.The entangled cavity state is reconstructed with only one atom interacting with the two cavities successively.
Zhong, Zhi-Rong
2008-05-01
An alternative scheme to approximately conditionally teleport entangled two-mode cavity state without Bell state measurement in cavity QED is proposed. The scheme is based on the resonant interaction of a ladder-type three-level atom with two bimodal cavities. The entangled cavity state is reconstructed with only one atom interacting with the two cavities successively.
Experimental Studies of NGNP Reactor Cavity Cooling System With Water
Corradini, Michael; Anderson, Mark; Hassan, Yassin; Tokuhiro, Akira
2013-01-16
This project will investigate the flow behavior that can occur in the reactor cavity cooling system (RCCS) with water coolant under the passive cooling-mode of operation. The team will conduct separate-effects tests and develop associated scaling analyses, and provide system-level phenomenological and computational models that describe key flow phenomena during RCCS operation, from forced to natural circulation, single-phase flow and two-phase flow and flashing. The project consists of the following tasks: Task 1. Conduct separate-effects, single-phase flow experiments and develop scaling analyses for comparison to system-level computational modeling for the RCCS standpipe design. A transition from forced to natural convection cooling occurs in the standpipe under accident conditions. These tests will measure global flow behavior and local flow velocities, as well as develop instrumentation for use in larger scale tests, thereby providing proper flow distribution among standpipes for decay heat removal. Task 2. Conduct separate-effects experiments for the RCCS standpipe design as two-phase flashing occurs and flow develops. As natural circulation cooling continues without an ultimate heat sink, water within the system will heat to temperatures approaching saturation , at which point two-phase flashing and flow will begin. The focus is to develop a phenomenological model from these tests that will describe the flashing and flow stability phenomena. In addition, one could determine the efficiency of phase separation in the RCCS storage tank as the two-phase flashing phenomena ensues and the storage tank vents the steam produced. Task 3. Develop a system-level computational model that will describe the overall RCCS behavior as it transitions from forced flow to natural circulation and eventual two-phase flow in the passive cooling-mode of operation. This modeling can then be used to test the phenomenological models developed as a function of scale.
Jazayeri, Amir M
2016-01-01
Optomechanics of nanoparticles purports to reach the quantum regime, but experimental evidence suggests otherwise. We believe that the discrepancy is due to the omission of the deleterious effects of the EM field levitating the particle. This letter focuses on quantum fluctuations in the levitating field. In a cavity-assisted system, they lead to fluctuations in the gradient force, and encourage escape of the particle. In a feedback system, they lead to the detector shot noise besides fluctuations in the gradient force and radiation pressure, and render the system very vulnerable to the thermal noise of the feedback circuit.
Structure an dynamics in cavity quantum electrodynamics
Much of the theoretical background related to the radiative processes for atoms in the presence of boundaries comes from two often disjoint areas, namely cavity quantum electrodynamics and optical bistability with two-state atoms. While the former of these areas has been associated to a large degree with studies in a perturbative domain of altered associated to a large degree with studies in a perturbative domain of altered emission processes in the presence of boundaries other than those of free space, the latter is often viewed from the perspective of hysteresis cycles and device applications. With the exception of the laser, however, perhaps the most extensive investigations of quantum statistical processes in quantum optics are to be found in the literature on bistability with two-state atoms and on cavity QED. Unfortunately, the degree of overlap of these two areas has not always been fully appreciated. This circumstance is perhaps due in part to the fact that the investigation of dynamical processes in cavity QED has had as its cornerstone the Jaynes-Cummings problem, with extensions to include, for example, small amounts of dissipation. On the other hand, a principle aspect of the bistability literature has been the study of quantum fluctuations in open systems for which dissipation plays a central role, but for which the coherent quantum dynamics of the Haynes-Cummings model are to a large measure lost due to the usual assumption of large system size and weak coupling (as in the standard theory of the laser). 132 refs., 26 figs., 1 tab
Dynamically controlling the emission of single excitons in photonic crystal cavities
Pagliano, Francesco; Xia, Tian; van Otten, Frank; Johne, Robert; Fiore, Andrea
2014-01-01
Single excitons in semiconductor microcavities represent a solid-state and scalable platform for cavity quantum electrodynamics (c-QED), potentially enabling an interface between flying (photon) and static (exciton) quantum bits in future quantum networks. While both single-photon emission and the strong coupling regime have been demonstrated, further progress has been hampered by the inability to control the coherent evolution of the c-QED system in real time, as needed to produce and harness charge-photon entanglement. Here, using the ultrafast electrical tuning of the exciton energy in a photonic crystal (PhC) diode, we demonstrate the dynamic control of the coupling of a single exciton to a PhC cavity mode on a sub-ns timescale, faster than the natural lifetime of the exciton, for the first time. This opens the way to the control of single-photon waveforms, as needed for quantum interfaces, and to the real-time control of solid-state c-QED systems.
Bistability and Entanglement of a Two-Mode Cavity Optomechanical System
Yousif, Taha; Zhou, Wenjun; Zhou, Ling
2016-02-01
We investigate the bistable properties and the entanglement in a two-mode cavity optomechanical system. Our results show that the bistable regime in terms of pumping amplitude can be adjusted by tuning the detunning. Although the two modes of the cavity interact with the same mechanical mode, there is no entanglement between them, while the two modes entangle with the mechanical mode seperately.
A temperature-mapping system for multi-cell SRF accelerating cavities
Ge, M; Furuta, F; Smith, E; Liepe, M; Posen, S; Padamsee, H; Hartill, D; Mi, X
2015-01-01
A Temperature mapping (T-map) system for Superconducting Radio Frequency (SRF) cavities consists of a thermometer array positioned precisely on an exterior cavity wall, capable of detecting small increases in temperature; therefore it is a powerful tool for research on the quality factor (Q0) of SRF cavities. A new multi-cell T-mapping system is has been developed at Cornell University. The system has nearly two thousand thermometers to cover 7-cell SRF cavities for Cornell ERL project. A new multiplexing scheme was adopted to reduce number of wires. A 1mK resolution of the temperature increase Delta T is achieved. A 9-cell cavity of TESLA geometry was tested with the T-map system. By converting Delta T to power loss and quality factor, it has been found that for this cavity, most surface losses were generated by the first cell when the accelerating gradient is increased above 15MV/m. The comparison of Q-value between with and without hotspots shows the heating on cavity wall degraded cavity Q0 about 1.65 tim...