Storage and Retrieval of a Squeezed Vacuum

Honda, K.; Akamatsu, Daisuke; Arikawa, Masatoshi; Yokoi, Yoshihiko; Akiba, Kenichi; Nagatsuka, Satoshi; Tanimura, Takahito; Furusawa, Akira; Kozuma, Mikio

doi:10.1103/physrevlett.100.093601

Cited by 247 publications

(208 citation statements)

References 25 publications

(40 reference statements)

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“…The expected values for the measured fidelities reasonably appear to pass our test, even though we judge that the challenge of a clear-cut demonstration of quantum teleportation of squeezed light, which likely appears within reach, is not closed yet. Regarding quantum memories, two recent experiments dealt with storage and retrieval of squeezed states using electromagnetically induced transparency [18,28]. In particular, in [18] the fidelity F = (89±1)% is reported for squeezed thermal input states with µ ≈ 0.66, neatly surpassing our upper bound on the average CFT.…”

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confidence: 86%

Quantum Benchmark for Teleportation and Storage of Squeezed States

Adesso

Chiribella

2008

Phys. Rev. Lett.

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We provide a quantum benchmark for teleportation and storage of single-mode squeezed states with zero displacement and completely unknown degree of squeezing along a given direction. For pure squeezed input states, a fidelity higher than 81.5% has to be attained in order to outperform any classical strategy based on estimation of the unknown squeezing and repreparation of squeezed states. For squeezed thermal input states, we derive an upper and a lower bound on the classical average fidelity, which tighten for moderate degree of mixedness. These results enable a critical discussion of recent experiments with squeezed light. Quantum entanglement is the key resource that allows a sender (Alice) and a receiver (Bob) to beat any classical strategy for transmitting and storing quantum states. In realistic implementations, however, the quality of transfer/storage is limited by factors such as imperfections and losses. To decide whether an experiment demonstrates a genuinely quantum feature, one needs appropriate figures of merit and appropriate benchmarks in terms of them. The typical figure of merit characterizing quantum teleportation (from now on we restrict to this protocol, bearing in mind that our results equally apply to state storage too) is the fidelity [10]between the unknown input state ̺ in to be teleported by Alice and the output state ̺ out which is actually obtained by Bob. To conclude that a quantum demonstration has taken place, the fidelity F has to beat the best possible fidelity F cl -usually called classical fidelity threshold (CFT)-achievable by two cheating parties who have access to unlimited "classical" means (local operations and classical communication) but are not able to share entanglement, nor to directly transmit quantum systems [11]. Under this restriction, the only possibility for Alice and Bob is a "measure-and-prepare" strategy, where Alice measures the input system and communicates the outcome to Bob, who prepares the output according to her prescription. Devising the CFT is hence a problem of quantum estimation [12].In the CV setting, the CFT has been only assessed for the special instance of pure coherent input states [11,13]. In the limit case of completely unknown coherent amplitude, it yields the benchmark F cl coh = 1/2, which has been extensively employed to validate experiments [7,8,9]. However, no such threshold is known for the case of squeezed states, which are currently drawing attention as input states of transfer protocols: the high-fidelity teleportation of squeezed states may enable cascading of teleportation, resulting in the construction of non-Gaussian gates (e.g. the cubic phase gate), useful to achieve universal CV quantum computation [6]. The lack of a CFT for squeezed states makes the validation of experiments a rather controversial issue, as there is no clear way to establish whether the achieved performances are signatures of a genuinely quantum information processing.In this Letter we provide the first quantum benchmark for teleportation and storage of sin...

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confidence: 86%

Quantum Benchmark for Teleportation and Storage of Squeezed States

Adesso

Chiribella

2008

Phys. Rev. Lett.

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“…The main objective is to store and retrieve light pulses or photons without destroying their quantum state, that is the system should be able to store at the same time two on commuting variables like the two quadratures of a light pulses and allow for their retrieval. Mapping quantum states of light like single photons or qubits [7][8][9], coherent light pulses without noise added [10] and squeezed light [11,12] onto long lived states of atomic coherence has been first experimentally investigated in alkali-metal gases. More recently quantum memory for entangled photons have been demonstrated in rare-earth doped crystals [13,14].…”

Section: Introductionmentioning

confidence: 99%

High-speed spatially multimode atomic memory

et al. 2011

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We study the coherent storage and retrieval of a very short multimode light pulse in an atomic ensemble. We consider a quantum memory process based on the conversion of a signal pulse into a long-lived spin coherence via light matter interaction in an on-resonant Λ -type system. In order to study the writing and reading processes we analytically solve the partial differential equations describing the evolution of the field and of the atomic coherence in time as well as in space. We show how to optimize the process for writing as well as for reading. If the medium length is fixed, for each length, there is an optimal value of the pulse duration. We discuss the information capacity of this memory scheme and we estimate the number of transverse modes that can be stored as a quantum hologram.

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“…For the storage and retrieval of entangled squeezed light they observed a 2.2 µs delay. In [31] was experimentally shown the storage and retrieval of the squeezed state using EIT in a sample of cold rubidium-87 atoms. The squeezed vacuum pulse had a temporal width of 930 ns and the obtained delay was of 3 µs.…”

Section: Introduction Backgroundmentioning

confidence: 99%