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arXiv:1608.07920 · Physical Review A

Generation of an optical Schrödinger-cat-like state in a nonideal cavity by injecting opposite-phase atomic dipoles

Daeho Yang, Junki Kim, Moonjoo Lee, Young-Tak Chough, Kyungwon An

Published Aug 15, 2016• 2 citations
arXivHTMLPDF

Abstract

We propose a method for generating an optical Schr\"odinger-cat-like state in a cavity in a substantial decoherence regime. Even when the cavity decay rate is considerably large, a cat-like state can be generated in a laser-like setting if the gain for the field is larger than the loss. Under the condition that opposite-phase atomic dipoles repeatedly traverse the cavity, the cavity field converges to a squeezed vacuum state in a steady state. A Schr\"odinger-cat-like state is then generated when a single photon decay occurs. The phase-space distribution of the cat state can be revealed in homodyne detection by using the decaying photon as a herald event. Quantum trajectory simulation was used to identify the conditions for the Schr\"odinger-cat-like state formation as well as to analyze the properties of those states. Based on these simulations, possible experiments are proposed within the reach of the current technology.

DOI
10.1103/physreva.94.023826

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We propose a method for generating an optical Schr"odinger-cat-like state in a cavity in a substantial decoherence regime. Even when the cavity decay rate is considerably large, a cat-like state can be generated in a laser-like setting if the gain for the field is larger than the loss. Under the condition that opposite-phase atomic dipoles repeatedly traverse the cavity, the cavity field converges to a squeezed vacuum state in a steady state. A Schr"odinger-cat-like state is then generated when a single photon decay occurs. The phase-space distribution of the cat state can be revealed in homodyne detection by using the decaying photon as a herald event. Quantum trajectory simulation was used to identify the conditions for the Schr"odinger-cat-like state formation as well as to analyze the properties of those states. Based on these simulations, possible experiments are proposed within the reach of the current technology.
We propose to use cavity Rydberg electromagnetically induced transparency to generate Schrödinger cat states of optical photons. We predict that this should make it possible to generate states with relatively large mean photon numbers. With existing technology, mean photon numbers around 30 seem feasible. The main limitation is photon loss during the process, which generates the state. The ability to tune the strength of the photon loss caused by atomic spontaneous emission makes it possible to have little decoherence despite significant photon loss during the generation of the state.
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The interaction of an atom with both a quantized cavity field and an external classical driving field, the fields being degenerate in frequency, is studied in the regime where the atom and fields are highly detuned. The atom interacts dispersively with the quantized field but the classical driving field gives rise to the creation or destruction of photons conditional on the state of the atom. We show how this interaction can be used to generate coherent states of the cavity field and various forms of superpositions of macroscopically distinct states. This method is in contrast to the usual method used in microwave cavity QED of injecting a coherent state into a cavity via a waveguide attached to a klystron and where subsequently Schr\"odinger cat states may be generated by manipulating the field with injected atoms. The method proposed here could possibly be used in the case of an optical cavity. Further, we show that coherent states may be generated in the steady state from the competition between the driven dispersion interaction and dissipative single-photon losses, a form of optical balance.
A scheme for generating Schr\"odinger-cat-like states of a single-mode optical field by means of conditional measurement is proposed. Feeding a squeezed vacuum into a beam splitter and counting the photons in one of the output channels, the conditional states in the other output channel exhibit a number of properties that are very similar to those of superpositions of two coherent states with opposite phases. We present analytical and numerical results for the photon-number and quadrature-component distributions of the conditional states and their Wigner and Husimi functions. Further, we discuss the effect of realistic photocounting on the states.
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