Arbitrarily Loss-Tolerant Einstein-Podolsky-Rosen Steering Allowing a Demonstration over 1 km of Optical Fiber with No Detection Loophole

Bennet, Adam; Evans, D. A.; Saunders, D. J.; Branciard, Cyril; Cavalcanti, Eric G.; Wiseman, Howard Mark; Pryde, Geoff J.

doi:10.1103/physrevx.2.031003

Cited by 160 publications

(149 citation statements)

References 37 publications

(55 reference statements)

Supporting

Mentioning

148

Contrasting

Order By: Relevance

“…This is readily verified by considering that (17b) can be saturated, as argued at the end of the previous section (see (18)), for an optimal solution of the SDP problem. So we have that for some deterministic D(a|x, λ) and some uncorrelated input state |φ to the channel, Considering also the subchannels Λ a , a = |A| + 1, .…”

Section: Details Of the Proof Of Theoremmentioning

confidence: 78%

“…For example, by exploiting steering it is possible to obtain key rates unachievable in a full device-independent approach [11], but still assuming less about the devices than in a standard QKD approach [12]. For these reasons, steering has attracted a lot of interest in recent times, both theoretically and experimentally [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], mostly directed to the verification of steering. Nonetheless, an answer to the question "What is steering useful for?"…”

mentioning

confidence: 99%

See 1 more Smart Citation

Necessary and Sufficient Quantum Information Characterization of Einstein-Podolsky-Rosen Steering

2015

View full text Add to dashboard Cite

Steering is the entanglement-based quantum effect that embodies the "spooky action at a distance" disliked by Einstein and scrutinized by Einstein, Podolsky, and Rosen. Here we provide a necessary and sufficient characterization of steering, based on a quantum information processing task: the discrimination of branches in a quantum evolution, which we dub subchannel discrimination. We prove that, for any bipartite steerable state, there are instances of the quantum subchannel discrimination problem for which this state allows a correct discrimination with strictly higher probability than in absence of entanglement, even when measurements are restricted to local measurements aided by one-way communication. On the other hand, unsteerable states are useless in such conditions, even when entangled. We also prove that the above steering advantage can be exactly quantified in terms of the steering robustness, which is a natural measure of the steerability exhibited by the state. Not all entangled states are steerable, and not all steerable states exhibit nonlocality [4,5], but states that exhibit steering allow for the verification of their entanglement in a semi-device independent way: there is no need to trust the devices used by the steering party, and the ability to determine the conditional states of the steered party is sufficient [4,5,9]. In general, besides its foundational interest, steering is interesting in practice in bipartite tasks, like quantum key distribution (QKD) [10], where it is convenient and/or appropriate to trust the devices of one of two parties, but not necessarily of the other party. For example, by exploiting steering it is possible to obtain key rates unachievable in a full device-independent approach [11], but still assuming less about the devices than in a standard QKD approach [12]. For these reasons, steering has attracted a lot of interest in recent times, both theoretically and experimentally [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], mostly directed to the verification of steering. Nonetheless, an answer to the question "What is steering useful for?" that applies to states that exhibit steering can arguably be considered limited [9,12]. Furthermore, the quantification of steering has just started to be addressed [24].In this Letter we fully characterize and quantify steering in an operational way that nicely matches the asymmetric features of steering, and that breaks new ground in the investigation of the usefulness of steering. We prove that every steerable state is a resource in a quantum information task that we dub subchannel discrimination, in a practically relevant scenario where measurements can only be performed locally.Subchannel discrimination is the identification of which branch of a quantum evolution a quantum system undergoes (see Fig. 1). It is well known that entanglement between a probe and an ancilla can help in discriminating different channels [31][32][33][34][35][36][37][38][39][40][41]. In [42] it was proven that actually every ...

show abstract

Section: Details Of the Proof Of Theoremmentioning

confidence: 78%

mentioning

confidence: 99%

Necessary and Sufficient Quantum Information Characterization of Einstein-Podolsky-Rosen Steering

2015

View full text Add to dashboard Cite

show abstract

“…Moreover, quantum steering was shown to be useful for one-sided device independent quantum key distribution (1SDIQKD) [13] and randomness certification [14]. Several experimental groups have recently observed steering, including in continuous-variable systems [15,16], using Bell local states [17], using inefficient detectors [18][19][20], asymmetric states [21], and multipartite systems [22][23][24].The main result of our paper is a general and optimal method to quantify the amount of local or global randomness that can be certified from a single measurement in a steering experiment. We use this method to OPEN ACCESS RECEIVED…”

mentioning

confidence: 99%

Optimal randomness certification in the quantum steering and prepare-and-measure scenarios

et al. 2015

View full text Add to dashboard Cite

Quantum mechanics predicts the existence of intrinsically random processes. Contrary to classical randomness, this lack of predictability can not be attributed to ignorance or lack of control. Here we find the optimal method to quantify the amount of local or global randomness that can be extracted in two scenarios: (i) the quantum steering scenario, where two parties measure a bipartite system in an unknown state but one of them does not trust his measurement apparatus, and (ii) the prepare-andmeasure scenario, where additionally the quantum state is known. We use our methods to compute the maximal amount of local and global randomness that can be certified by measuring systems subject to noise and losses and show that local randomness can be certified from a single measurement if and only if the detectors used in the test have detection efficiency higher than 50%.One of the most distinct features of quantum mechanics is its intrinsically random character. While in classical mechanics lack of predictability can always be associated to ignorance or lack of control of the probed systems, the rules of quantum physics say that one can not predict the outcome of a measurement even if all the variables of a system are known. This inherent unpredictability has been exploited in different applications such as quantum random number generation [1] and quantum key distribution [2].Recent results have shown that the randomness observed in quantum mechanics can be certified even without relying on any modelling of the quantum devices used for the generation of the random data. In fact, by analysing the data obtained in experiments involving local measurements on bipartite entangled systems one can prove that no one could have predicted this data in advance whenever a Bell inequality violation is observed [3,4]. This is called device-independent (DI) randomness certification [5,6]. The DI approach has the practical advantage that it does not rely on the exact description of the experimental set-up. This is crucial when implementing cryptographic protocols as an adversary can use a mismatch between the theoretical description and the actual implementation of the set-up to fake its performance [7][8][9]. However, DI protocols require low levels of noise [4], which make them very demanding experimentally.An intermediate scenario is that of quantum steering [10,11]. It refers to the case where two parties, say Alice and Bob, apply local measurements on an unknown bipartite system. While one of them, Bob, has complete knowledge of his measurement apparatuses, Alice does not, and treats her measuring device as a black box with classical inputs and outputs. Quantum steering has been receiving lot of attention recently due to the fact that it allows for entanglement detection which is more robust to noise and experimental imperfections than Bell nonlocality [11,12]. Moreover, quantum steering was shown to be useful for one-sided device independent quantum key distribution (1SDIQKD) [13] and randomness certification [14]. Several expe...

show abstract

“…Several experiments have been already performed, demonstrating steering and its asymmetry [21,22,[25][26][27][28][29][30][31], and a number of recent studies have been devoted to improving our understanding of quantum steerability, ranging from the development of better criteria to detect steerable states [32][33][34][35][36], to the analysis of the distribution of steering among multiple parties [37][38][39][40]. However, unlike entanglement, for which a variety of operationally motivated measures exist [6,41], there is still a surprisingly scarce literature addressing the fundamental question of quantifying how steerable a given quantum state is [11,23,42].…”

mentioning

confidence: 99%

Quantification of Gaussian Quantum Steering

et al. 2015

View full text Add to dashboard Cite

Einstein-Podolsky-Rosen steering incarnates a useful nonclassical correlation which sits between entanglement and Bell nonlocality. While a number of qualitative steering criteria exist, very little has been achieved for what concerns quantifying steerability. We introduce a computable measure of steering for arbitrary bipartite Gaussian states of continuous variable systems. For two-mode Gaussian states, the measure reduces to a form of coherent information, which is proven never to exceed entanglement, and to reduce to it on pure states. We provide an operational connection between our measure and the key rate in one-sided device-independent quantum key distribution. We further prove that Peres' conjecture holds in its stronger form within the fully Gaussian regime: namely, steering bound entangled Gaussian states by Gaussian measurements is impossible. Steering is the quantum mechanical phenomenon that allows one party, Alice, to change (i.e., to "steer") the state of a distant party, Bob, by exploiting their shared entanglement. This phenomenon, fascinatingly discussed by Schrödinger [8,9], was already noted by Einstein, Podolksy, and Rosen (EPR) in their famous 1935 paper [12], and is at the heart of the so-called EPR paradox [13]. There it was argued that steering implied an unacceptable "action at a distance," which led EPR to claim the incompleteness of quantum theory. The EPR expectations for local realism were mostly extinguished by Bell's theorems [14,15], which showed that no locally causal theory can reproduce all the correlations observed in nature [16]. The first experimental criterion for the demonstration of the EPR paradox, i.e., for the detection of quantum steering, was later proposed by Reid [17], but it was not until 2007 that the particular type of nonlocality captured by the concept of steering [8,9,12] was in fact formalized [10,18].From a quantum information perspective [10], steering corresponds to the task of verifiable entanglement distribution by an untrusted party. If Alice and Bob share a state which is steerable in one way, say from Alice to Bob, then Alice is able to convince Bob (who does not trust Alice) that their shared state is entangled, by performing local measurements and classical communication [10]. Notice that steering, unlike entanglement, is an asymmetric property: a quantum state may be steerable from Alice to Bob, but not vice versa. On the operational side, it has been recently realized that steering provides security in one-sided device-independent quantum key distribution (QKD) [19], where the measurement apparatus of one party only is untrusted. These protocols are less demanding than totally device-independent ones, for which Bell nonlocality is known to be necessary [3]. Experimentally, at variance with the case of Bell tests, a demonstration of steering free of detection and locality loopholes is in reach [19][20][21][22], which makes one-sided device-independent QKD appealing for current technology and quantum steering a practically useful concept. EPR ste...

show abstract

Arbitrarily Loss-Tolerant Einstein-Podolsky-Rosen Steering Allowing a Demonstration over 1 km of Optical Fiber with No Detection Loophole

Cited by 160 publications

References 37 publications

Necessary and Sufficient Quantum Information Characterization of Einstein-Podolsky-Rosen Steering

Necessary and Sufficient Quantum Information Characterization of Einstein-Podolsky-Rosen Steering

Optimal randomness certification in the quantum steering and prepare-and-measure scenarios

Quantification of Gaussian Quantum Steering

Contact Info

Product

Resources

About