Distinguishing Quantum and Classical Many-Body Systems

TL;DR

This paper presents a protocol to verify quantum entanglement in many-body systems, enabling confirmation of quantum behavior without full classical simulation, by testing for non-local correlations through a derived inequality.

Contribution

The authors develop a general protocol and inequality for detecting entanglement in many-body systems, applicable to quantum simulators and other complex quantum models.

Findings

Protocol can verify entanglement between distant parts of a many-body system.

Derived inequality analogous to Bell's inequality for local testing.

Example provided in quantum magnetism demonstrating the protocol.

Abstract

Controllable systems relying on quantum behavior to simulate distinctly quantum models so far rely on increasingly challenging classical computing to verify their results. We develop a general protocol for confirming that an arbitrary many-body system, such as a quantum simulator, can entangle distant objects. The protocol verifies that distant qubits interacting separately with the system can become mutually entangled, and therefore serves as a local test that excitations of the system can create non-local quantum correlations. We derive an inequality analogous to Bell's inequality which can only be violated through entanglement between distant sites of the many-body system. Although our protocol is applicable to general many-body systems, it requires finding system-dependent local operations to violate the inequality. A specific example in quantum magnetism is presented.