The IBM Quantum and IonQ devices turn out to be sufficiently accurate to pass an extended Bell‐type test of local realism focusing on the objectivity criterion, although at the price of communication loopholes and residual but statistically significant signaling.
Abstract
We have constructed and run a Bell test of local realism focusing on the objectivity criterion. Objectivity means that the outcomes are macroscopically confirmed by a few observers at each party. The IBM Quantum and IonQ devices turn out to be sufficiently accurate to pass such an extended Bell‐type test, although at the price of communication loopholes and residual but statistically significant signaling. The test also serves as a benchmark of entanglement spread across larger sets of qubits.
Quantum Fisher information (QFI) is a fundamental quantity in quantum information and quantum mechanics, and evaluating it in various physical systems has become an important research topic. However, its evaluation in large systems still faces many challenges. Hereby we propose an ancilla-based protocol for evaluating...
We recently proposed an entanglement distillation protocol based on local operations and classical communication that probabilistically and universally distills a maximally entangled Bell pair from multiple copies of an unknown two-qubit state [Phys. Rev. Lett. 135, 260202 (2025)]. Here, we investigate the robustness o...
The violation of Bell-like inequalities unambiguously verifies the entanglement of a multipartite quantum state. However, experimental impairments and nonidealities often compromise the entanglement quality, and this degradation translates into a nonmaximal violation of these inequalities. We present a detailed analysi...
Richard A. Brewster, J. Goldhar, M. Morris et al.· IEEE Transactions on Quantum...· 0 citations
A fundamental prediction of quantum mechanics is that observables can be measured through ideal measurements, that is, measurements that give the same outcome when repeated and do not disturb any observable that is jointly measurable. In terms of quantum instruments, such an ideal measurement is described by projective...
We prove Shor's conjecture: an orthogonal measurement maximizes the information obtainable from any two quantum states in finite dimension. We then show that an error constraint can require three outcomes. For a class of full-rank qubit pairs, the best orthogonal basis switches abruptly as the error penalty increases....
