Testing quantum contextuality of continuous-variable states

McKeown, Gerard; Paris, Matteo G. A.; Paternostro, Mauro

doi:10.1103/physreva.83.062105

Cited by 14 publications

(11 citation statements)

References 42 publications

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“…2 (b), we plot the optimal phase estimation as a function of N av , for the phase averaged states in Eqs. ( 13) and (15). We see that the enhancement of the optimal phase estimation is similar to the behavior shown in Fig.…”

Section: Generation Schemesupporting

confidence: 78%

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Quantum phase estimation using a multi-headed cat state

Lee

Nha

et al. 2015

J. Opt. Soc. Am. B

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It was recently shown that an entangled coherent state, which is a superposition of two different coherent states, can surpass the performance of noon state in estimating an unknown phase-shift. This may hint at further enhancement in phase estimation by incorporating more component states in the superposition of resource state. We here introduce a four-headed cat state (4HCS), a superposition of four different coherent states, and propose its application to quantum phase estimation. We demonstrate the enhanced performance in phase estimation by employing an entangled state via the 4HCS, which can surpass that of the two-headed cat state (2HCS), particularly in the regime of small average photon numbers. Moreover, we show that an entangled state modified from the 4HCS can further enhance the phase estimation, even in the regime of large average photon number under a photon-loss channel. Our investigation further extends to incorporate an increasingly large number of component states in the resource superposition state and clearly show its merit in phase estimation.

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Section: Generation Schemesupporting

confidence: 78%

“…There are also probabilistic heralding schemes using photon subtraction or homodyne detections [11,12]. ECSs have a wide scope of applications ranging from fundamental tests of quantum mechanics [13][14][15][16] to practical quantum computation [17][18][19][20][21][22][23], communication [24][25][26], and metrology [27,28].…”

Section: Introductionmentioning

confidence: 99%

Quantum phase estimation using a multi-headed cat state

Lee

Nha

et al. 2015

J. Opt. Soc. Am. B

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“…Schrödinger cat states, superpositions of two coherent states with coherent amplitudes of the same magnitude but different phases, have been widely studied for the significant role they could play in quantum information [1][2][3][4][5], computation [6,7] and in fundamental tests [8][9][10][11] as resource states. For example Ralph et al [3] showed that cat states can be used to implement qubit gates in an all optical quantum computation scheme, where the logical qubits are encoded in the phase of the coherent state complex amplitude and Jeong [8] considered the possibility of testing the Bell inequalities using cat-like states as resources.…”

Section: Introductionmentioning

confidence: 99%

Parity-swap state comparison amplifier for Schrödinger cat states

2021

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We propose a postselecting parity-swap amplifier for Schrödinger cat states that does not require the amplified state to be known a priori. The device is based on a previously-implemented state comparison amplifier for coherent states. It consumes only Gaussian resource states, which provides an advantage over some cat state amplifiers. It requires simple Geiger-mode photodetectors and works with high fidelity and approximately twofold gain.

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“…Coherent state superpositions, or optical Schrödinger cat states, are widely recognized as promising resources in quantum information [1][2][3][4][5], quantum metrology [6][7][8], and fundamental tests [9][10][11][12]. In the near-orthogonal basis of coherent states γ|−γ = e −2γ 2 , two particular instances for these states are…”

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confidence: 99%

Amplification of realistic Schrödinger-cat-state-like states by homodyne heralding

Laghaout

Neergaard-Nielsen

Rigas³

et al. 2013

Phys. Rev. A

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We present a scheme for the amplification of Schrödinger cats that collapses two smaller states onto their constructive interference via a homodyne projection. We analyze the performance of the amplification in terms of fidelity and success rate when the input consists of either exact coherent state superpositions or of photon-subtracted squeezed vacua. The impact of imprecise homodyne detection and of impure squeezing is quantified. We also assess the scalability of iterated amplifications.Coherent state superpositions, or optical Schrödinger cat states, are widely recognized as promising resources in quantum information [1][2][3][4][5], quantum metrology [6][7][8], and fundamental tests [9][10][11][12]. In the near-orthogonal basis of coherent states γ|−γ = e −2γ 2 , two particular instances for these states arewhere the sign (±) of the superposition refers to the even and odd cat state, respectively. These states exhibit quasi-probability distributions in phase space which are distinctly non-classical. This makes them all the more challenging to generate deterministically as that would require strong Kerr-type non-linearities [13][14][15].One has then to resort to heralding techniques which, though probabilistic, need only linear optics and projective measurements [16]. These state-engineering schemes are nonetheless approximative and present a limitation in the fidelity they produce with ideal cat states. Photon-subtraction of squeezed vacuum, for example, is a well-established method to generate approximations of small amplitude cat states, colloquially referred to as Schrödinger kittens [17][18][19][20][21]. Even in the best experimental conditions, the fidelity between the photon-subtracted squeezed vacuum (PSSV) and an actual odd cat state |κ − (γ) degrades markedly for γ ≥ 1.2 [22]. Yet, for these states to be reliable resources in quantum computation, their fidelity with cat states at least as large as γ = 1.2 need to be maintained at near-unit fidelity [3,23]. Single-photon subtraction is only one example of several measurement-induced schemes which have been proposed to generate kitten states [20,[24][25][26][27][28][29]. However, none of these schemes can produce arbitrarily large cats in a single run. Ways to get around this issue have been devised using the recursive amplification of small, approximate cats [30,31]. For example, it was suggested in [32] to interfere a supply of delocalized single photons followed by homodyne heralding to generate large entangled cat states. These proposals have in common that they rely on the coherent mixing of two small cats, whereupon a projective measurement collapses one of the two outputs onto a constructive interference of the inputshence the amplification. Here, we shall pursue the same idea but make use solely of homodyne heralding for its relative simplicity and high quantum efficiency. We also demonstrate that the acceptance window of homodyne heralding can be widened to increase the success rate of the amplification while at the same time maintaining a s...

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Testing quantum contextuality of continuous-variable states

Cited by 14 publications

References 42 publications

Quantum phase estimation using a multi-headed cat state

Quantum phase estimation using a multi-headed cat state

Parity-swap state comparison amplifier for Schrödinger cat states

Amplification of realistic Schrödinger-cat-state-like states by homodyne heralding

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