ISSN:0950-0340    

DOI:10.1080/09500349708231863

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The dynamics of quantum decoherence have been experimentally studied for the first time. A single circular Rydberg atom prepares in a high-quality superconducting cavity a ‚Schrödinger cat’ state of the radiation field. This highly non-classical state is a quantum superposition of two coherent components with different classical phases. A second atom probes the cavity state after a tunable delay. The decay of the quantum correlations between the two atoms reveals the evolution of the initial quantum superposition into a mere statistical mixture. The time scale of this process decreases when the separation beween the two components increases. A simple theoretical model of the experiment is presented. The excellent agreement with the experimental signals confirms in a striking way the decoherence approach.

ISSN:0950-0340    

DOI:10.1080/09500349708231864

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A feedback model based on direct photodetection and micromaser-like atomic injection is proposed for the preservation of quantum coherence in a cavity. We show that in this way it is possible to slow down significantly the decoherence of Schrödinger cat states.

ISSN:0950-0340    

DOI:10.1080/09500349708231865

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

It is shown that the decoherence of the Yurke–Stoler coherent state of a field in an open cavity can be significantly slowed down when the feedback is organized between the outgoing radiation and the intracavity field.

ISSN:0950-0340    

DOI:10.1080/09500349708231866

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The effect of quantum dispersion (i.e. a multitude of quantum states corresponding to each value of an observable) on laboratory feedback optimal control is studied. It is shown by numerical and analytical means that including the variance of the observable in the objective functional as well as the presence of modest noise in the controls can steer the system into a low-variance quantum state or, if possible, into an eigenstate of the observable.

ISSN:0950-0340    

DOI:10.1080/09500349708231867

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The active microcavity is adopted as an efficient source of non-classical light. By this device, excited by a mode-locked laser at a rate of 100 MHz, single photons are generated over asinglefield mode with a non-classical sub-Poissonian distribution. The process of adiabatic recycling within a multistep Franck–Condon molecular optical-pumping mechanism, characterized in our case by a quantum efficiency close to one, implies a pump self-regularization process leading to a strikingn-squeezing effect. Moreover, the microactivity has been adopted asactive beam splitterin a novel Hanbury-Brown–Twiss configuration for the radiation taking place over the two output mirrors. By a replication of the basic single-atom excitation process a beam of quantum photon |n⟩ states (Fock states) can be created. The new process may represent a significant advance in the modern fields of basic quantum-mechanical investigation, quantum communication and quantum cryptography.

ISSN:0950-0340    

DOI:10.1080/09500349708231868

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We report a high efficiency scheme for generating a single-photon state transmitted out of an optical cavity. For realistic cavity QED parameters, we show that the scheme can produce a single-photon pulse with a probability exceeding 99% in a user-specified time interval. By recycling the system, the scheme can be used to create a bit-stream of single-photon pulses.

ISSN:0950-0340    

DOI:10.1080/09500349708231869

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We present the theory underlying a new experimental scheme for the preparation of selected number states of a bimodal high-Qmicrocavity. The practical feasibility of this method is carefully discussed. In particular we take explicitly into account the existence of fluctuations of the atom–field interaction times as well as the possibility of imperfect atomic detection.

ISSN:0950-0340    

DOI:10.1080/09500349708231870

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A conditional generation of single-mode Fock states in the framework of a non-degenerate two-photon micromaser theory is reported. The exact expression for the probability of success of the experiment is obtained. We show that it is possible to conjugate experimentally interesting values of this probability, with the generation of number states having a controllable high intensity. This objective is reached by constructing analytically detailed rules about the cavity state att= 0 as well as the atom–field interaction times as functions of the available operating conditions. These rules play a central role in our Fock-state-building process, leading to an essential countering of the Stark-shift-induced detuning effects. The practical reliability of the proposal is carefully discussed from several points of view. Some possible applicative potentialities of our scheme are briefly pointed out.

ISSN:0950-0340    

DOI:10.1080/09500349708231871

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We discuss a model of a cavity filled with a passive nonlinear ‚Kerr’ medium and periodically kicked by a series of ultra-short laser pulses. The nonlinear medium is described by the (2q− 1)th nonlinearityX(2q−1). We find analytical formulas describing the field states inside the cavity. We show that such a system can produce, depending on the order of the nonlinearity, superpositions of several Fock states with the small photon numbers (0,1; 0,1,2; etc). In particular, the one-photon state can be approached during the evolution of the system withX(3)nonlinearity provided the cavity losses are negligible. The purity of states generated in this process, however, can be seriously degraded by the cavity damping. We perform numerical calculations to validate our analytical results.

ISSN:0950-0340    

DOI:10.1080/09500349708231872

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor