The Leggett-Garg inequality attempts to classify experimental outcomes as arising from one of two possible classes physical theories: those described by macrorealism (which obey our intuition about how the macroscopic classical world behaves), and that are not (e.g., quantum theory). development cloud-based computing devices enables us explore limits in new regimes. In particular, here we take advantage properties programmable nature IBM experience observe violation (in form a ``quantum...

Quantum channels breaking entanglement, incompatibility, or nonlocality are defined as such because they not useful for entanglement-based, one-sided device-independent, device-independent quantum-information processing, respectively. Here, we show that related to complementary tests of macrorealism, i.e., temporal separability, channel unsteerability, and the Bell inequality. To demonstrate this first define a steerability-breaking channel, which is conceptually similar entanglement...

Quantum steering is the central resource for one-sided device-independent quantum information. It manipulated via one-way local operations and classical communication, such as filtering on trusted party. Here, we provide a necessary sufficient condition assemblage to be transformable into another one filtering. We characterize equivalence classes with respect filters in terms of equivalent observables measurement (SEO), first proposed connect problem steerability incompatibility. an...

Quantum steering is an important correlation in quantum information theory. A recent work [Nat. Commun. 12, 2410 (2021)] showed that also useful for metrology. Here, we extend the exploration of steering-enhanced metrology from single noiseless phase shifts to superpositions noisy shifts. As concrete examples, consider a control system manipulates target pass through superposition either dephased or depolarized channels. We show using such can suppress effects noise and improve Furthermore,...

Abstract Open quantum systems are susceptible to losses in information, energy, and particles due their surrounding environment. One novel strategy mitigate these is transform them into advantages for technologies through tailored non-Hermitian systems. In this work, we theoretically propose a fast generation of multipartite entanglement qubits. Our findings reveal that weakly coupled qubits can accelerate multiparty by thousands times compared Hermitian qubits, particular when approaching...

The uncertainty principle is one of quantum theory's most foundational features. It underpins a phenomenon called measurement incompatibility—two physical observables single system may not always be measured simultaneously. Apart from being fundamentally important, incompatibility also powerful resource in the broad science and technologies, with wide applications to cryptography, communication, random number generation, device-independent tasks. Since every unavoidably subject noise, an yet...

We propose a measure of quantum steerability, namely, convex steering monotone, based on the trace distance between given assemblage and its corresponding closest admitting local-hidden-state (LHS) model. provide methods to estimate such quantity, via lower upper bounds, semidefinite programming. One these bounds has clear geometrical interpretation as linear function rescaled Euclidean distances in Bloch sphere normalized states (i) (ii) an LHS assemblage. For qubit-qubit state, ideas also...

Einstein-Podolsky-Rosen (EPR) steering is an intermediate quantum correlation that lies in between entanglement and Bell non-locality. Its temporal analogue, steering, has recently been shown to have applications information open systems. Here, we show there exists a hierarchy among the three correlations: inseparability, macrorealism. Given inseparability can be used define measure of causality, similarly quantification viewed as weaker direct cause distinguish common network.

Einstein-Podolsky-Rosen (EPR) steering allows Alice to remotely prepare a state in some specific bases for Bob through her choice of measurements. The temporal analogue EPR steering, also reveals the steerability single system between different times. Focusing on four-dimensional system, here we investigate dynamics measures, robustness, using 5 mutually unbiased bases. As an example application, use these measures examine correlations radical pair model magnetoreception. We find that, due...

Given a Bell inequality, if its maximal quantum violation can be achieved only by single set of measurements for each party or state, up to local unitaries, one refers such phenomenon as self-testing. For instance, the Clauser-Horne-Shimony-Holt inequality certifies that underlying state contains two-qubit maximally entangled and pair anti-commuting qubit observables. As consequence, other automatically verifies states remotely steered, namely "assemblage", is in eigenstates It natural ask...

Steering resources, central for quantum advantages in one-sided device-independent information tasks, can be enhanced via local filters. Recently, reversible steering conversion under filters has been fully characterised. Here, we solve the problem irreversible scenario, which leads to a complete understanding of stochastic distillation. This result also provides an operational interpretation max-relative entropy as optimal filter success probability. We further show that all measures used...

Entanglement-breaking channels (equivalently, measure-and-prepare channels) are an important class of quantum operations noted for their ability to destroy multipartite spatial correlations. Inspired by this property, they have also been employed in defining notions "classical memory", under the assumption that such effectively act as a classical resource. We show that, single-system multi-time scenario, entanglement-breaking still memory resource: qudit going through channel cannot be...

We show that the incompatibility of a set measurements cannot be increased by subjecting them to filter, namely, combining with device post-selects incoming states on fixed outcome stochastic transformation. This result holds for several measures incompatibility, such as those based robustness and convex weight. Expanding these ideas Einstein-Podolsky-Rosen steering experiments, we are able solve problem maximum steerability obtained respect most general local filters in way allows an...

One-way quantum computing is a promising candidate for fault-tolerant computing. Here, we propose protocols to realize deterministic one-way controlled-not (cnot) gate and $X$ rotations on current quantum-computing platforms. By applying delayed-choice scheme, overcome limit of most currently available computers, which are unable implement further operations measured qubits or conditioned measurement results from other qubits. Moreover, decrease the error rate logic gates, compared original...

Abstract Within the framework of quantum refereed steering games, steerability can be certified without any assumption on underlying state nor measurements involved. Such a scheme is termed measurement-device-independent (MDI) scenario. Here, we introduce measure in an MDI scenario, i.e., result merely depends observed statistics and inputs. We prove that such satisfies convex monotone. Moreover, it robust against not only measurement biases but also losses. experimentally estimate amount...

To store quantum information, memory plays a central intermediate ingredient in network. The minimal criterion for reliable is the maintenance of entangled state, which can be described by non-entanglement-breaking (non-EB) channel. In this work, we show that all single-qubit quantified without trusting input state generation. other words, provide semi-device-independent approach to quantify memory. More specifically, apply concept two-qubit steering ellipsoids channel and define ellipsoids....

The inevitable noise within one-sided device-independent quantum information tasks may completely break any steering resources. These noisy effects are characterized by the steerability breaking (SB) channels. In this work, we demonstrate use of a control system that can superpose $N$ copies given SB channel to activate channels such becomes non-SB one. particular, analytically and numerically show depolarizing amplitude-damping be coherently activated when $N\ensuremath{\ge}2$. addition,...

The interplay between thermal machines and quantum correlations is of great interest in both thermodynamics information science. Recently, a Szil\'ard engine has been proposed, showing that the steerability Maxwell's demon work medium can be beneficial to extraction task. Nevertheless, this type quantum-fueled machine usually fragile presence decoherence effects. We provide an example pure dephasing process, engine's quantumness degraded. Therefore, work, we tackle question by introducing...

Entanglement lies at the heart of quantum mechanics, and has been identified an essential resource for diverse applications in information. If entanglement could be verified without any trust devices observers, i.e., a device-independent (DI) way, then unconditional security can guaranteed various information tasks. In this work, we propose experimental-friendly DI protocol to certify presence entanglement, based on Einstein-Podolsky-Rosen (EPR) steering. We first establish verification...

Quantum state transfer (QST) provides a method to send arbitrary quantum states from one system another. Such concept is crucial for transmitting information into the memory, processor, and network. The standard benchmark of QST average fidelity between prepared received states. In this work we provide new which reveals nonclassicality based on spatiotemporal steering (STS). More specifically, show that local-hidden-state (LHS) model in STS can be viewed as classical strategy transfer....

Quantum information scrambling describes the delocalization of local to global in form entanglement throughout all possible degrees freedom. A natural measure is tripartite mutual information, which quantifies amount delocalized for a given quantum channel with its state representation, i.e., Choi state. In this work, we show that can also be witnessed by temporal steering qubit systems. We do so because there fundamental equivalence between and pseudodensity matrix formalism used...

Open quantum systems are susceptible to losses in information, energy, and particles due their surrounding environment. One novel strategy mitigate these is transform them into advantages for technologies through tailored non-Hermitian systems. In this work, we theoretically propose a fast generation of multipartite entanglement qubits. Our findings reveal that weakly coupled qubits can accelerate multiparty by thousands times compared Hermitian qubits, particular when approaching the...

The uncertainty principle is one of quantum theory's most foundational features. It underpins a phenomenon called measurement incompatibility -- two physical observables single system may not always be measured simultaneously. Apart from being fundamentally important, also powerful resource in the broad science and technologies, with wide applications to cryptography, communication, random number generation, device-independent tasks. Since every unavoidably subject noise, an yet still open,...