Witnesses of coherence and dimension from multiphoton indistinguishability tests

Giordani, Taira; Esposito, Chiara; Hoch, Francesco; Carvacho, Gonzalo; Brod, Daniel J.; Galvão, Ernesto F.; Spagnolo, Nicolò; Sciarrino, Fabio

doi:10.1103/physrevresearch.3.023031

Cited by 10 publications

(8 citation statements)

References 52 publications

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“…In Methods and note S1, we recall why the overlap inequalities of ( 17 , 20 ) serve as set coherence witnesses. The first nontrivial inequality bounding coherence [Galv 17] was experimentally investigated in ( 18 ) and bounds the three overlaps of a set of three statesr0,1+r0,2−r1,2≤1…”

Section: Resultsmentioning

confidence: 99%

“…We prove that the inequality violated by pure qutrits cannot be violated by qubits, complementing this result with numerical and experimental investigations, and we perform a similar analysis for our inequalities violated by ququart and ququint systems. In doing so, we extend the dimension witness result from ( 18 ) both qualitatively and quantitatively, making the best use of the flexibility and accuracy of our multimode processor.…”

Section: Introductionmentioning

confidence: 97%

“…In this work, we propose and test families of coherence and contextuality witnesses in proof-of-principle device-dependent experiments carried out with single-photon states processed by a programmable integrated photonic circuit. These witnesses require the careful preparation of the system in a set of different states and then the estimation of a set of pairwise state overlaps (17)(18)(19)(20). For this task, we encode qubits and qudits with dimensions up to five in a six-mode universal photonic processor (UPP) realized with the femtosecond laser writing technology (21).…”

Section: Introductionmentioning

confidence: 99%

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Experimental certification of contextuality, coherence, and dimension in a programmable universal photonic processor

Giordani,

Wagner,

Esposito

et al. 2023

Sci. Adv.

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Quantum superposition of high-dimensional states enables both computational speed-up and security in cryptographic protocols. However, the exponential complexity of tomographic processes makes certification of these properties a challenging task. In this work, we experimentally certify coherence witnesses tailored for quantum systems of increasing dimension using pairwise overlap measurements enabled by a six-mode universal photonic processor fabricated with a femtosecond laser writing technology. In particular, we show the effectiveness of the proposed coherence and dimension witnesses for qudits of dimensions up to 5. We also demonstrate advantage in a quantum interrogation task and show it is fueled by quantum contextuality. Our experimental results testify to the efficiency of this approach for the certification of quantum properties in programmable integrated photonic platforms.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Experimental certification of contextuality, coherence, and dimension in a programmable universal photonic processor

Giordani,

Wagner,

Esposito

et al. 2023

Sci. Adv.

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“…where each |v l , λ v l v l , λ v l | or |w l , λ w l w l , λ w l | corresponds to the state of the system after a measurement (related to observable V or W) has been performed on it and an outcome (v l , λ v l ) or (w l , λ w l ) has been obtained. As we will see shortly, the various fundamental concepts discussed so far-namely, the KD distribution in equation ( 3), its extended version in equation ( 4), the quasiprobability behind the OTOC in equation (11), the post-selected quantum Fisher information in equation (5), and the expression for weak values in equation ( 2)-are all written in terms of Bargmann invariants, which we review next.…”

Section: Otocsmentioning

confidence: 99%

Quantum circuits for measuring weak values, Kirkwood–Dirac quasiprobability distributions, and state spectra

Wagner,

Schwartzman-Nowik,

Paiva

et al. 2024

Quantum Sci. Technol.

Self Cite

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Weak values and Kirkwood--Dirac (KD) quasiprobability distributions have been independently associated with both foundational issues in quantum theory and advantages in quantum metrology. We propose simple quantum circuits to measure weak values, KD distributions, and spectra of density matrices without the need for post-selection. This is achieved by measuring unitary-invariant, relational properties of quantum states, which are functions of Bargmann invariants, the concept that underpins our unified perspective. Our circuits also enable experimental implementation of various functions of KD distributions, such as out-of-time-ordered correlators (OTOCs) and the quantum Fisher information in post-selected parameter estimation, among others. An upshot is a unified view of nonclassicality in all those tasks. In particular, we discuss how negativity and imaginarity of Bargmann invariants relate to set coherence.

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“…Here we will consider the relative purity f (ρ, ) := Tr(ρ ) as a natural distinguishability measure of two quantum states [29]. Importantly, such an informationtheoretic quantifier has been useful in the study of quantum speed limits [30][31][32][33], information scrambling and Loschmidt echoes [34,35], and also for probing quantum coherence from photonic metrological setups [36]. While not being a distance in the stringent sense, the relati-ve purity is symmetric, f (ρ, ) = f ( , ρ), non-negative, f (ρ, ) ≥ 0, for all states ρ and , and vanishes for the case in which the states are maximally distinguishable.…”

Section: Relative Purity and Equilibrationmentioning

confidence: 99%

Relative purity, speed of fluctuations, and bounds on equilibration times

Pires,

de Oliveira

2021

Preprint

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We discuss the local equilibration of closed systems using the relative purity, a paradigmatic information-theoretic distinguishability measure that finds applications ranging from quantum metrology to quantum speed limits. First we obtain a upper bound on the average size of the fluctuations on the relative purity: it depends on the effective dimension resembling the bound obtained with the trace distance. Second, we investigate the dynamics of relative purity and its rate of change as a probe of the speed of fluctuations around the equilibrium. In turn, such speed captures the notion of how fast some nonequilibrium state approaches the steady state under the local nonunitary dynamics, somehow giving the information of the quantum speed limit (QSL) towards the equilibration. We show that the size of fluctuations depends on the quantum coherences of the initial state with respect to the eigenbasis of the Hamiltonian, also addressing the role played by the correlations between system and reservoir into the averaged speed. Finally, we have derived a family of lower bounds on the time of evolution between these states, thus obtaining an estimate for the equilibration time at the local level. These results could be of interest to the subjects of equilibration, quantum speed limits, and also quantum metrology.

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Witnesses of coherence and dimension from multiphoton indistinguishability tests

Cited by 10 publications

References 52 publications

Experimental certification of contextuality, coherence, and dimension in a programmable universal photonic processor

Experimental certification of contextuality, coherence, and dimension in a programmable universal photonic processor

Quantum circuits for measuring weak values, Kirkwood–Dirac quasiprobability distributions, and state spectra

Relative purity, speed of fluctuations, and bounds on equilibration times

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