Entanglement of a Mesoscopic Field with an Atom Induced by Photon Graininess in a Cavity

Auffèves, Alexia; Maioli, Paolo; Meunier, Tristan; Gleyzes, Sébastien; Brune, M.; Raimond, Jean‐Michel; Haroche, S.

doi:10.1103/physrevlett.91.230405

Cited by 163 publications

(152 citation statements)

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“…We have checked that the splitting is proportional to t i and inversely proportional to α. The observed phase shifts are in good agreement with the simple first order calculation presented above and in excellent agreement with a numerical simulation of the exact atom-cavity interaction [43]. The maximum phase splitting, for n = 15 and t i = 52 µs, was 90 • , a phase space separation much larger than what can be obtained in the dispersive regime.…”

Section: Observing the Field Phase Separationsupporting

confidence: 76%

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Monitoring the Decoherence of Mesoscopic Quantum Superpositions in a Cavity

Raimond

Haroche

2006

Quantum Decoherence

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Abstract. Decoherence is an extremely fast and efficient environment-induced process transforming macroscopic quantum superpositions into statistical mixtures. It is an essential step in quantum measurement and a formidable obstacle for a practical use of quantum superpositions (quantum computing for instance). For large objects, decoherence is so fast that its dynamics is unobservable. Mesoscopic fields stored in a high-quality superconducting millimeter-wave cavity, a modern equivalent to Einstein's 'photon box', are ideal tools to reveal the dynamics of the decoherence process. Their interaction with a single circular Rydberg atom prepares them in a quantum superposition of fields, containing a few photons, with different classical phases. The evolution of this 'Schrödinger cat' state can be later probed with a 'quantum mouse', another atom, assessing its coherence. We describe here the experiments performed along these lines at ENS, and stress the deep links between decoherence and complementarity.

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Section: Observing the Field Phase Separationsupporting

confidence: 76%

“…We have evidenced the resonant phase separation via a measurement of the final field phase distribution [43]. The experiment is similar to the measurement of the dispersive phase shifts described above.…”

Section: Observing the Field Phase Separationmentioning

confidence: 56%

Monitoring the Decoherence of Mesoscopic Quantum Superpositions in a Cavity

Raimond

Haroche

2006

Quantum Decoherence

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“…Indeed, by applying a simple displacement operation on the field operators in the form a → b = a − / g, we can shift the initial state to a coherent state and transform atomic pumping to cavity driving. Hence the dynamics is mathematically equivalent to the case of a cavity-driven Jaynes-Cummings model with the field initially in a coherent state [9], and the scheme closely resembles recent experiments performed in the microwave regime by Auffeves et al [10]. They were able to generate and study large-amplitude coherent-state superpositions by similar means.…”

mentioning

confidence: 68%

“…This is experimentally challenging. There is, however, an alternative procedure, also used in the microwave regime [10]. Here one just time-reverses the generation process by applying a proper phase shift to the atomic ground state and sending a second pulse.…”

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confidence: 99%

Deterministic generation of tailored-optical-coherent-state superpositions

2004

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Pulsed coherent excitation of a two-level atom strongly coupled to a resonant cavity mode will create a superposition of two coherent states of opposite amplitudes in the field. By choosing proper parameters of interaction time and pulse shape the field after the pulse will be almost disentangled from the atom and can be efficiently outcoupled through cavity decay. The fidelity of the generation approaches unity if the atom-field coupling strength is much larger than the atomic and cavity decay rates. This implies a strong difference between even and odd output photon number counts. Alternatively, the coherence of the two generated field components can be proven by phase-dependent annihilation of the generated nonclassical superposition state by a second pulse. . Recently, it has been noted that such states could also be used in quantum-information processing for encoding qubits in the relative phase of the two classical amplitude [3]. In principle they allow quantum teleportation and linear quantum gates in a straightforward manner [4]. Although nondeterministic sources could be used for these applications it would clearly be more desirable if a controlled deterministic source was available in the optical domain.Nonlinear optical setups, such as, e.g., a subthreshold optical parametric oscillator or electrically induced transparency type interactions in atomic media, have been suggested as possible sources of such states [5]. Alternatively, traveling-wave coherent-superposition states might be generated by sending a three-level atom in a superposition state of the two lower levels through a high-Q cavity, which couples only one of the levels with a third upper state [6]. The desired quantum state is then generated by sending a light pulse through the cavity followed by postselection on the outcome of a subsequent proper projective measurement on the atom. In this way, the microscopic quantum superposition of the atom is transformed to a macroscopic superposition of the light field being transmitted or reflected from the cavity. Although this scheme works well in principle it is slow and hard to implement in practice.Here we propose a significantly simpler version of a cavity QED scheme using just a two-level atom resonantly coupled to a single mode of a high-Q cavity mode with a coupling strength g exceeding the natural linewidth ␥ of the atomic transition and the cavity decay rate (Fig. 1). All that is needed is to apply a coherent driving pulse of proper strength and duration to the atom from the side. The induced Rabi flopping of the atom together with coherent scattering of the pulse light into the cavity mode then generate the desired field state. Interestingly, it is possible to tailor the interaction time in such a way that the atom gets disentangled from the field after the pulse so that no projective measurement on the atom is required. This is a central difference from previous suggestions of using a far-detuned pulse. Such a pulse creates a similar field, but as it induces no atomic transitions it le...

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“…Not all initial quantum states are equally fragile to this interaction: often there are relatively robust states with respect to it, called "pointer states" [4]. Experimental evidence of this environment induced decoherence has also been recently reported [5,6,7,8,9].…”

Section: Introductionmentioning

confidence: 99%

Loss of coherence and dressing in QED

Bellomo

Petruccione

2006

Phys. Rev. A

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The dynamics of a free charged particle, initially described by a coherent wave packet, interacting with an environment, i.e. the electromagnetic field characterized by a temperature T , is studied. Using the dipole approximation the exact expressions for the evolution of the reduced density matrix both in momentum and configuration space and the vacuum and the thermal contribution to decoherence, are obtained. The time behaviour of the coherence lengths in the two representations are given. Through the analysis of the dynamic of the field structure associated to the particle the vacuum contribution is shown to be linked to the birth of correlations between the single momentum components of the particle wave packet and the virtual photons of the dressing cloud.

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Entanglement of a Mesoscopic Field with an Atom Induced by Photon Graininess in a Cavity

Cited by 163 publications

References 20 publications

Monitoring the Decoherence of Mesoscopic Quantum Superpositions in a Cavity

Monitoring the Decoherence of Mesoscopic Quantum Superpositions in a Cavity

Deterministic generation of tailored-optical-coherent-state superpositions

Loss of coherence and dressing in QED

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