There is more to quantum interferometry than entanglement

Bromley, Thomas R.; Silva, Isabela A.; Segura, Charlie Oncebay; Soares-Pinto, Diogo O.; deAzevedo, Eduardo R.; Tufarelli, Tommaso; Adesso, Gerardo

doi:10.1103/physreva.95.052313

Cited by 16 publications

(17 citation statements)

References 81 publications

(156 reference statements)

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“…In particular, they both obey all Requirements (i)-(iv) [54,57], while Requirement (v) is currently being tested, with some partial progress achieved for Q C QF Γ A (ρ AB ) [67]. By construction, it holds…”

Section: 84mentioning

confidence: 99%

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Measures and applications of quantum correlations

Adesso¹,

Bromley²,

Cianciaruso³

2016

J. Phys. A: Math. Theor.

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397

416

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Abstract. Quantum information theory is built upon the realisation that quantum resources like coherence and entanglement can be exploited for novel or enhanced ways of transmitting and manipulating information, such as quantum cryptography, teleportation, and quantum computing. We now know that there is potentially much more than entanglement behind the power of quantum information processing. There exist more general forms of non-classical correlations, stemming from fundamental principles such as the necessary disturbance induced by a local measurement, or the persistence of quantum coherence in all possible local bases. These signatures can be identified and are resilient in almost all quantum states, and have been linked to the enhanced performance of certain quantum protocols over classical ones in noisy conditions. Their presence represents, among other things, one of the most essential manifestations of quantumness in cooperative systems, from the subatomic to the macroscopic domain. In this work we give an overview of the current quest for a proper understanding and characterisation of the frontier between classical and quantum correlations in composite states. We focus on various approaches to define and quantify general quantum correlations, based on different yet interlinked physical perspectives, and comment on the operational significance of the ensuing measures for quantum technology tasks such as information encoding, distribution, discrimination and metrology. We then provide a broader outlook of a few applications in which quantumness beyond entanglement looks fit to play a key role.

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Section: 84mentioning

confidence: 99%

“…, with Υ being either a unitary operation or unitarily equivalent to transposition (see [67] for further details on these channels, including their Kraus operator sum representation), or completely decohering maps.…”

Section: Requirements For a Bona Fide Measure Of Quantum Correlationsmentioning

confidence: 99%

Measures and applications of quantum correlations

Adesso¹,

Bromley²,

Cianciaruso³

2016

J. Phys. A: Math. Theor.

Self Cite

397

416

View full text Add to dashboard Cite

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“…(20) to obtain the QFI of a single-mode Gaussian state ρ A . We will get an expression which is equivalent, but not identical, to the one found in Ref.…”

Section: B Gaussian States Of Continuous Variable Systemsmentioning

confidence: 99%

“…(20), in order to obtain an expression for the QFI of a single-mode probe, labeled by H (1) . With the former choice, this becomes …”

Section: B Gaussian States Of Continuous Variable Systemsmentioning

confidence: 99%

“…This is because any local probe undergoing a unitary evolution is left unchanged by a Hamiltonian diagonal in its same eigenbasis and the worst-case precision becomes trivially zero. Although entangled states guarantee the highest minimal precision, interestingly the presence of entanglement is not a necessary condition in order to obtain a nonzero worst-case performance [18][19][20][21]. Indeed, the key resource in this and similar discrimination tasks is a weaker form of correlation known as "quantum discord" [22,23].…”

Section: Introductionmentioning

confidence: 99%

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Versatile Gaussian probes for squeezing estimation

et al. 2017

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We consider an instance of "black-box" quantum metrology in the Gaussian framework, where we aim to estimate the amount of squeezing applied on an input probe, without previous knowledge on the phase of the applied squeezing. By taking the quantum Fisher information (QFI) as the figure of merit, we evaluate its average and variance with respect to this phase in order to identify probe states that yield good precision for many different squeezing directions. We first consider the case of single-mode Gaussian probes with the same energy, and find that pure squeezed states maximize the average quantum Fisher information (AvQFI) at the cost of a performance that oscillates strongly as the squeezing direction is changed. Although the variance can be brought to zero by correlating the probing system with a reference mode, the maximum AvQFI cannot be increased in the same way. A different scenario opens if one takes into account the effects of photon losses: coherent states represent the optimal single-mode choice when losses exceed a certain threshold and, moreover, correlated probes can now yield larger AvQFI values than all single-mode states, on top of having zero variance.

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