arXiv subjects

Sanchit Srivastava

Publications and source records attributed to Sanchit Srivastava.

5 recordsLinked to original sources

arXiv2025

Multipartite entanglement vs nonlocality for two families of $N$-qubit states

Entangled states of multiple qubits can violate Bell-type inequalities indicating nonlocal behavior of multiqubit quantum correlations. We analyze the relation between multipartite entanglement and genuine multipartite nonlocality, characterized by Svetlichny inequality violations, for two families of $N-$qubit states. We show that for the generalized GHZ family of states, Svetlichny inequality is not violated when the $n-$tangle is less than $1/2$ for any even number of qubits. On the other hand, the maximal slice states always violate the Svetlichny inequality when $n-$tangle is nonzero, and the violation increases monotonically with tangle. Our work generalizes the relations between tangle and Svetlichny inequality violations previously derived for three qubits.

quant-ph↗

arXiv2025

Contextuality from the vacuum

Contextuality, a key resource for quantum advantage, describes systems in which the outcome of a measurement is not independent of other compatible measurements, in contrast to classical hidden-variable descriptions. We investigate the harvesting of contextuality from the vacuum of a quantum field using Unruh-DeWitt detectors. We show that localized interactions with the field can endow initially non-contextual detectors with contextuality with respect to Heisenberg-Weyl measurements, as quantified by contextual fraction. The harvested contextuality correlates with the emergence of Wigner function negativity, in agreement with known equivalences between these notions. Our results show that contextuality is a resource that can be extracted directly from the quantum vacuum and establish contextuality harvesting as a fundamental phenomenon in relativistic quantum information.

quant-ph↗

arXiv2025

Contextuality and Chaos

Classical chaos is marked by an extreme sensitivity to initial conditions, where infinitesimally close trajectories separate exponentially over time. In quantum mechanics, however, unitary evolution and the uncertainty principle preclude such behavior, necessitating alternative approaches to identifying chaos in quantum systems. One must therefore seek quantum features that can indicate the emergence of chaos in the classical limit. Here, we show that contextuality, a quantum property that defies classical explanations, can serve as a signature of chaos. For a spin system undergoing chaotic dynamics, we demonstrate that violations of Bell-type inequality can effectively differentiate regular and chaotic regions of the phase space, suggesting that the nonclassicality of the system underpins signatures of chaos.

quant-ph↗

arXiv2024

Non-classical correlations between a quantum probe and complex quantum systems in presence of noise

Non-classical correlations generated within a quantum probe system when it interacts with a large, macroscopic system can signal the presence of quantum features in the latter. Theoretical models have considered how entanglement generated in photosynthetic bacteria can be probed using light that interacts with them. More recently, a tardigrade was entangled to a transmon qubit. We consider a detailed model including noise for such systems wherein a small quantum probe interacts with a large system in order to delineate the regimes with respect to coupling strengths and noise levels in which such signatures of quantumness in macroscopic systems can realistically be detected.

quant-ph↗

arXiv2021

Simulating quantum chaos on a quantum computer

We show that currently available noisy intermediate-scale quantum (NISQ) computers can be used for versatile quantum simulations of chaotic systems. We introduce a novel classical-quantum hybrid approachfor exploring the dynamics of the chaotic quantum kicked top (QKT) on a universal quantum computer. The programmability of this approach allows us to experimentally explore the complete range of QKT chaoticity parameter regimes inaccessible to previous studies. Furthermore, the number of gates in our simulation does not increase with the number of kicks, thus making it possible to study the QKT evolution for arbitrary number of kicks without fidelity loss. Using a publicly accessible NISQ computer (IBMQ), we observe periodicities in the evolution of the 2-qubit QKT, as well as signatures of chaos in the time-averaged 2-qubit entanglement. We also demonstrate a connection between entanglement and delocalization in the 2-qubit QKT, confirming theoretical predictions.

quant-ph↗