Simulating the Interplay of Particle Conservation and Long-Range Coherence

Area of Science:

• Quantum physics
• Atomic physics
• Quantum computing

Background:

• Lasers and Bose-Einstein condensates (BECs) display macroscopic quantum coherence through different mechanisms.
• Lasers have a defined global phase with fluctuating photon numbers.
• BECs conserve particle number but lack a defined global phase.

Purpose of the Study:

• To establish a unified quantum circuit framework connecting lasers and BECs.
• To develop a scalable circuit for measuring particle number without losing coherence.
• To investigate the impact of particle number measurement on phase coherence.

Main Methods:

• Utilized gate-based quantum circuits for a unified theoretical framework.
• Implemented a scalable circuit to measure total particle number.
• Introduced complementary probes for global and relative phase coherence.
• Performed experiments on a Rigetti superconducting quantum computer.

Main Results:

• Demonstrated that particle conservation strengthens long-range phase coherence in BECs.
• Showcased the effect of particle number measurements on coherence probes.
• Successfully implemented coherence probes on superconducting quantum hardware.

Conclusions:

• Particle conservation is a key mechanism for enhancing phase coherence, as seen in superfluids and superconductors.
• The quantum circuit framework provides a novel connection between laser and BEC physics.
• Superconducting quantum computers are viable platforms for exploring fundamental quantum phenomena.