Optical phase estimation via the coherent state and displaced-photon counting

Izumi, Shuro; Takeoka, Masahiro; Wakui, Kentaro; Fujiwara, Mikio; Ema, Kazuhiro; Sasaki, Masahide

doi:10.1103/physreva.94.033842

Cited by 22 publications

(17 citation statements)

References 39 publications

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“…For simplicity of the analysis, we consider only two outcomes: zero photons in both detectors or other events, {|0 0|⊗|0 0|, I −|0 0|⊗|0 0|} (photon number discrimination may further improve the performance but to simplify the discussion here, we leave it for a future work). Note that this mirror-image like detection strategy has been considered in the context of state 5 discrimination [18,19] and also the phase estimation via coherent-state input [20]. Since we need the phase information of the input state at the anti-squeezing process, this is a phase-sensitive measurement, and so the POVM has access to external phase information and the phase of the squeezerŜ † .…”

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confidence: 99%

Fundamental precision limit of a Mach-Zehnder interferometric sensor when one of the inputs is the vacuum

et al. 2017

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In the lore of quantum metrology, one often hears (or reads) the following no-go theorem: If you put vacuum into one input port of a balanced Mach-Zehnder Interferometer, then no matter what you put into the other input port, and no matter what your detection scheme, the sensitivity can never be better than the shot noise limit (SNL). Often the proof of this theorem is cited to be in Ref. [C. Caves, Phys. Rev. D 23, 1693(1981], but upon further inspection, no such claim is made there. A quantum-Fisher-information-based argument suggestive of this no-go theorem appears in Ref. [M. Lang and C. Caves, Phys. Rev. Lett. 111, 173601 (2013)], but is not stated in its full generality. Here we thoroughly explore this no-go theorem and give the rigorous statement: the nogo theorem holds whenever the unknown phase shift is split between both arms of the interferometer, but remarkably does not hold when only one arm has the unknown phase shift. In the latter scenario, we provide an explicit measurement strategy that beats the SNL. We also point out that these two scenarios are physically different and correspond to different types of sensing applications.Introduction.-In the field of quantum metrology [1][2][3], a Mach-Zehnder interferometer (MZI) is a tried and true workhorse that has the additional advantage that any result obtained for it also applies to a Michelson interferometer (MI) and hence has a potential application to gravitational wave detection. In most current implementations of gravitational wave detectors, the MI is fed with a strong coherent state of light in one input port and vacuum in the other (Fig. 1). It was in this context that Caves in 1981 [4] showed that such a design would always only ever achieve the shotnoise limit (SNL). Then he showed if you put squeezed vacuum into the unused port, you could beat the SNL. Several implementations of this squeezed vacuum scheme have already been demonstrated in the GEO 600 gravitational detector, and plans are underway to utilize this approach in the LIGO and VIRGO detectors in the future [5,6].It then appeared, that in the lore of quantum metrology, this result was extended -without proof -to the following no-go theorem: If you put quantum vacuum into one input port of a balanced MZI, then no matter what quantum state of light you put into the other input port, and no matter what your detection scheme, the sensitivity can never be better than the SNL. Often the proof of this theorem is cited to be the original 1981 paper by Caves [4], but upon further inspection, no such general claim is made there. A quantum-Fisherinformation-based argument suggestive of this no-go theorem appeared in Ref. [7] by Lang and Caves, but it does not explore the statement in adequate generality.In this work, we give a full statement of the no-go theorem. The statement proved here is the following: if the unknown phase shifts are in both of the two arms of the MZI, then the no-go theorem holds no matter whether the MZI is balanced or not. However, in the case where the unknown phas...

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Fundamental precision limit of a Mach-Zehnder interferometric sensor when one of the inputs is the vacuum

et al. 2017

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“…Since our all-fiber-based telecom quantum receiver is compatible with current optical fiber communication and can be modified to another type of two-dimensional projector such as a single-rail qubit projector [25], we expect that our receiver will provide a practical advantage for not only conventional coherent communication but also quantum-optical information processing [40][41][42]. An interesting future step is to install our telecom quantum receiver in long-distance fiber communication systems by developing a truly local reference field for the displacement operation [43,44]. Such a realistic communication scenario requires high-speed transmission of signal states and therefore the bandwidth of the feedback operation would become a more-critical challenge to be overcome.…”

Section: Discussionmentioning

confidence: 96%

Experimental Demonstration of a Quantum Receiver Beating the Standard Quantum Limit at Telecom Wavelength

et al. 2020

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Discrimination of coherent states beyond the standard quantum limit (SQL) is an important task not only for quantum information processing but also for optical coherent communication. To optimize longdistance optical fiber networks, it is of practical importance to develop a quantum receiver beating the SQL and approaching the quantum bound at telecom wavelength. In this paper, we experimentally demonstrate a receiver beating the conventional SQL at telecom wavelength. Our receiver is composed of a displacement operation, a single-photon counter, and a real-time adaptive-feedback operation. By using a high-performance single-photon detector operating at the telecom wavelength, we achieve a discrimination error beyond the SQL. The demonstration in the telecom band is an enabler for quantum and classical communication beyond the SQL using a coherent state alphabet, and we envision that the technology can be used for long-distance quantum-key distribution, effective quantum-state preparation, and quantum estimation.

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“…Since our all-fiber-based telecom quantum receiver is compatible with current optical fiber communication and can be modified to another type of two-dimensional projector such as a single-rail qubit projector [23], we expect that our receiver will provide a practical advantage for not only conventional coherent communication but also quantum optical information processing [37][38][39]. An interesting future step is to install our telecom quantum receiver in long distance fiber communication systems by developing a truly local reference field for the displacement operation [40,41]. Such a realistic communication scenario requires high speed transmission of signal states and therefore the bandwidth of the feedback operation would become a more critical challenge to be overcome.…”

Section: Discussionmentioning

confidence: 96%

Experimental demonstration of a quantum receiver beating the standard quantum limit at the telecom wavelength

Izumi,

Neergaard-Nielsen,

Miki

et al. 2020

Preprint

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Discrimination of coherent states beyond the standard quantum limit (SQL) is an important task not only for quantum information processing but also for optical coherent communication. In order to optimize long distance optical fiber networks, it is of practical importance to develop a quantum receiver beating the SQL and approaching the quantum bound at telecom wavelength. In this paper, we experimentally demonstrate a receiver beating the conventional SQL at telecom wavelength. Our receiver is composed of a displacement operation, a single photon counter and a real time adaptive feedback operation. By using a high performance single photon detector operating at the telecom wavelength, we achieve a discrimination error beyond the SQL. The demonstration in the telecom band provides the first step important towards quantum and classical communication beyond the SQL using a coherent state alphabet, and we envision that the technology can be used for longdistance quantum key distribution, effective quantum state preparation and quantum estimation.

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Optical phase estimation via the coherent state and displaced-photon counting

Cited by 22 publications

References 39 publications

Fundamental precision limit of a Mach-Zehnder interferometric sensor when one of the inputs is the vacuum

Fundamental precision limit of a Mach-Zehnder interferometric sensor when one of the inputs is the vacuum

Experimental Demonstration of a Quantum Receiver Beating the Standard Quantum Limit at Telecom Wavelength

Experimental demonstration of a quantum receiver beating the standard quantum limit at the telecom wavelength

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