Sustained State-Independent Quantum Contextual Correlations from a Single Ion

Abstract

We use a single trapped-ion qutrit to demonstrate the quantum-state-independent violation of noncontextuality inequalities using a sequence of randomly chosen quantum nondemolition projective measurements. We concatenate 53×10^{6} sequential measurements of 13 observables, and unambiguously violate an optimal noncontextual bound. We use the same data set to characterize imperfections including signaling and repeatability of the measurements. The experimental sequence was generated in real time with a quantum random number generator integrated into our control system to select the subsequent observable with a latency below 50 μs, which can be used to constrain contextual hidden-variable models that might describe our results. The state-recycling experimental procedure is resilient to noise and independent of the qutrit state, substantiating the fact that the contextual nature of quantum physics is connected to measurements and not necessarily to designated states. The use of extended sequences of quantum nondemolition measurements finds applications in the fields of sensing and quantum information.

Optimal Classical Simulation of State-Independent Quantum Contextuality

“…These sets are called QSIC sets [21,22] and, for each of them, there are optimal combinations of correlations for detecting contextuality [15]. The interest of this case comes from the fact that unbounded strings of data with contextual correlations can be produced using a single system initially prepared in an arbitrary state [20], a situation that strongly contrasts with the case of nonlocality generated through the violation of a Bell inequality, where thousands of spacelike separated pairs of quantum systems in an entangled quantum state are needed. The question we want to address in this Letter is what is the minimal amount of memory a classical system would need to simulate the predictions of quantum theory for QSIC experiments with unlimited sequential measurements.…”

“…It inspired a photonic experiment by Zu et al [29] (see also Amselem et al [30]) and was implemented as an experiment with sequential measurements on a single ion by Zhang et al [31], and, recently, it was used to implement the scheme in Fig. 1 by Leupold et al [20].…”

“…A particularly interesting case is that of quantum state-independent contextuality (QSIC) in experiments with sequential measurements [12][13][14][15] on a single recycled quantum system [16,19,20]. In this case, a single quantum system is submitted to an unlimited sequence of measurements, randomly chosen from a finite set of measurements, as illustrated in Fig.…”

Genuine temporal correlations can certify the quantum dimension

“…Moreover, noncontextuality inequalities have been experimentally violated (see e.g. [5]). This triggered research on the question which temporal correlations can be realized within quantum mechanics [6][7][8][9][10].…”

Necessary and sufficient condition for contextuality from incompatibility

“…All these compatibility graphs can be realized in experiments with sequential measurements on single systems, such as the experiments of Refs. [46][47][48][49]. In addition, some of the compatibility graphs can be realized in multipartite scenarios, since their sets of vertices can be divided into disjoint subsets, each subset corresponding to the measurements of one party and containing some nonadjacent vertices (i.e., incompatible measurements), and such that each vertex in a subset is adjacent to all vertices in the other subsets.…”