Time-crystalline eigenstate order on a quantum processor

Area of Science:

• Quantum physics
• Condensed matter physics
• Quantum information science

Background:

• Quantum many-body systems exhibit complex phases at equilibrium.
• Non-equilibrium systems can host novel dynamical phases, like discrete time crystals (DTCs).
• Observing these dynamical phases experimentally is challenging due to transient behaviors.

Purpose of the Study:

• To experimentally observe a many-body localized discrete time crystal (MBL-DTC).
• To demonstrate the characteristic spatiotemporal response of MBL-DTCs for generic initial states.
• To establish a scalable method for studying non-equilibrium phases on quantum processors.

Main Methods:

• Implementation of tunable controlled-phase (CPHASE) gates on superconducting qubits.
• Utilizing a time-reversal protocol to assess decoherence effects.
• Employing quantum typicality to overcome challenges in spectral sampling.
• Conducting experimental finite-size analysis to locate phase transitions.

Main Results:

• Experimental observation of an MBL-DTC in a superconducting qubit array.
• Demonstration of the MBL-DTC's characteristic spatiotemporal response for generic initial states.
• Successful quantification of decoherence impact and location of the phase transition.

Conclusions:

• This work provides experimental evidence for MBL-DTCs as a distinct non-equilibrium phase.
• The developed methods offer a scalable approach for studying novel non-equilibrium phenomena.
• The findings advance the understanding of quantum phases beyond thermal equilibrium.