Experimental Generation of Quantum Discord via Noisy Processes

Lanyon, B. P.; Jurcevic, Petar; Hempel, Cornelius; Gessner, Manuel; Vedral, Vlatko; Blatt, R.; Roos, C. F.

doi:10.1103/physrevlett.111.100504

Cited by 64 publications

(80 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The improvement we predict is consistent with the capability of correlated noisy channels to bring about nonclassical features, as in [36]. In conclusion we have discussed how a physical property of photon pairs, namely their frequency correlations, should be taken into account when one studies their use for phase estimation.…”

Section: Resultssupporting

confidence: 60%

Monitoring dispersive samples with single photons: the role of frequency correlations

Roccia¹,

Genoni²,

Mancino³

et al. 2017

Quantum Measurements and Quantum Metrology

View full text Add to dashboard Cite

Abstract:The physics that governs quantum monitoring may involve other degrees of freedom than the ones initialised and controlled for probing. In this context we address the simultaneous estimation of phase and dephasing characterizing a dispersive medium, and we explore the role of frequency correlations within a photon pair generated via parametric down-conversion, when used as a probe for the medium. We derive the ultimate quantum limits on the estimation of the two parameters, by calculating the corresponding quantum Cramér-Rao bound; we then consider a feasible estimation scheme, based on the measurement of Stokes operators, and address its absolute performances in terms of the correlation parameters, and, more fundamentally, of the role played by correlations in the simultaneous achievability of the quantum Cramér-Rao bounds for each of the two parameters.Quantum light provides a gentler touch when observing fragile samples [1][2][3]. While typically all the information needed can be e ciently collected through a single parameter [4,5], there are instances in which two parameters or more are necessary to capture the physical process under study [6][7][8]. Such parameters might not be associated to compatible observables, hence trade-o may appear in attempts at simultaneously measuring them at the ultimate quantum precision, especially when restrictions are imposed on the resources or, in other words, to the available Hilbert space [7,[9][10][11][12][13][14][15] These trade-o can be interpreted, and often circumvented, by understanding the estimation process under the geometrical standpoint by identifying the physical carrier of information with their state vectors [13]; however, quantum probes only partly approximate such geometric entities, since these typically describe one degree of freedom at the time. The interaction with the sample might actually depend on other degrees of freedom, on which we might have limited control. A relevant example is given by dispersion e ects in phase estimation: if the phase under observation depends on the optical frequency of a photonic probe, the adoption of broad bandwidths would result in dephasing [13,[17][18][19]. An e cient way to tackle this is a joint estimation of the mean phase together with the characteristic width of the dephasing.Single photons from down-conversion are often employed as building blocks of quantum light probes [20][21][22][23][24]. These are produced in pairs that, under standard conditions, share frequency entanglement as a consequence of energy conservation in the generation process [25][26][27][28][29][30][31][32][33] . In this article we calculate what impact such frequency correlation might have on the joint estimation of phase and dephasing in dispersive elements. Our study found that di erences arise if one considers correlated and anticorrelated photon pairs, particularly showing how anticorrelated photons result as more interesting resources to be employed in such noisy phase estimation problem.The manuscript is organized as follows...

show abstract

Section: Resultssupporting

confidence: 60%

Monitoring dispersive samples with single photons: the role of frequency correlations

Roccia¹,

Genoni²,

Mancino³

et al. 2017

Quantum Measurements and Quantum Metrology

View full text Add to dashboard Cite

show abstract

“…There, particular attention was paid to the existence and robustness of so called decoherence free sub-spaces (DFS) under collective dephasing [25]. Moreover, recent studies [28,29] have shown that collective dephasing could also be used as a resource to generate strong but separable correlations. We note that, due to their promise as a general passive strategy to protect quantum resources from noise, the study of DFS continues to be an active area of research, see [30] for a recent review on the theoretical aspects and [31] for experimental implementations.…”

mentioning

confidence: 99%

“…The physical origin of collective dephasing is left unspecified in the theoretical treatment here. Note that it can, for instance, arise via correlated magnetic field fluctuations for ions [28] or due to interactions with phononic baths in the case of colour centers [23,36,37] (see [38] for additional details regarding such situations).…”

mentioning

confidence: 99%

Cooperative Effects in Closely Packed Quantum Emitters with Collective Dephasing

2018

View full text Add to dashboard Cite

In a closely packed ensemble of quantum emitters, cooperative effects are typically suppressed due to the dephasing induced by the dipole-dipole interactions. Here, we show that by adding sufficiently strong collective dephasing cooperative effects can be restored. In particular, we show that the dipole force on a closely packed ensemble of strongly driven two-level quantum emitters, which collectively dephase, is enhanced in comparison to the dipole force on an independent non-interacting ensemble. Our results are relevant to solid state systems with embedded quantum emitters such as colour centers in diamond and superconducting qubits in microwave cavities and waveguides. A collection of two-level quantum emitters (TLEs) with sub-wavelength average separations can show remarkable cooperative behaviour like superradiant emission [1][2][3]. The study of optical response in such systems has predominantly been restricted to the emission properties or the propagation of light within the TLE ensemble. This is because the systems usually considered in the early days [2,4], as well as in some recent works [5][6][7][8], are gaseous clouds of atoms. With the advent of artificial atoms in solid state systems, e.g. quantum dots [9], superconducting qubits [10,11] and colour centers in diamond [12][13][14], it is now possible to study the impact of cooperative effects on other aspects of the optical response. In particular, a recent experiment [13] studied the dipole force on optically trapped nanodiamonds containing a high density of Nitrogen vacancy (NVs) centers. An intriguing result in [13] was that the observed dipole force originating from the emitters could not be correctly accounted for by considering the emitters to respond independently.In this work, we focus on cooperative effects in a small and closely packed ensemble of TLEs subject to strong coherent driving and collective dephasing. In particular, we show that the dipole force on such an ensemble can be larger than on an equivalent one where each TLE spontaneously emits independently. For the emitter separations that we consider here, the dipole-dipole interaction can be larger than the line-width of the individual emitters. Furthermore, spontaneous emission is not perfectly collective. In this situation, one typically expects cooperative effects to be suppressed [2,15]. Here, we show that the combination of strong driving and large collective dephasing can restore cooperative effects, even in the presence of dipole interaction shifts and non-collective spontaneous emission. While there have been previous studies of cooperative effects with strong driving fields [16][17][18][19][20][21][22], the role of collective dephasing has received less attention [10,13]. In the context of Quantum Information, collective decoherence in general, and collective dephasing in particular, has been studied both theoretically [23][24][25] and experimentally [26,27]. There, particular attention was paid to the existence and robustness of so called decoherence free sub-spaces (D...

show abstract

“…Unlike entanglement, production of discord-like QCs is not demanding since they can be created from classicallycorrelated states via local noise [12][13][14][15][16], a situation forbidding any entanglement to arise. In this respect, a rather spectacular effect that might have profound technological developments is entanglement activation (EA) via discord [17][18][19][20] in a four-partite system.…”

Section: Introductionmentioning

confidence: 99%

Steady-state entanglement activation in optomechanical cavities

et al. 2014

View full text Add to dashboard Cite

Quantum discord, and related indicators, are raising a relentless interest as a novel paradigm of non-classical correlations beyond entanglement. Here, we discover a discord-activated mechanism yielding steady-state entanglement production in a realistic continuous-variable setup. This comprises two coupled optomechanical cavities, where the optical modes (OMs) communicate through a fiber. We first use a simplified model to highlight the creation of steady-state discord between the OMs. We show next that such discord improves the level of stationary optomechanical entanglement attainable in the system, making it more robust against temperature and thermal noise.

show abstract

Experimental Generation of Quantum Discord via Noisy Processes

Cited by 64 publications

References 32 publications

Monitoring dispersive samples with single photons: the role of frequency correlations

Monitoring dispersive samples with single photons: the role of frequency correlations

Cooperative Effects in Closely Packed Quantum Emitters with Collective Dephasing

Steady-state entanglement activation in optomechanical cavities

Contact Info

Product

Resources

About