Time Crystals as Passively Protected Oscillating Qubits

TL;DR

This paper demonstrates that driven-dissipative bosonic systems can encode and passively protect oscillating qubits using time-crystalline dynamics, offering a new approach to error-resilient quantum information storage.

Contribution

It introduces a novel scheme where a Bose-Hubbard dimer encodes a persistently oscillating qubit within a noiseless subsystem through dissipative time-crystalline behavior.

Findings

Persistent oscillations encode quantum information.

Oscillating qubits are robust against global loss and dephasing.

Phase perturbations are passively corrected, maintaining qubit coherence.

Abstract

Protecting information against decoherence in open quantum systems remains a central challenge for quantum computing. In particular, passive error correction schemes have so far been limited to static memories rather than dynamical qubits. We demonstrate that a driven-dissipative bosonic system can encode a persistently oscillating qubit within a noiseless subsystem, realized explicitly in the Bose-Hubbard dimer (BHD). The strong parity symmetry of the model leads to degenerate stationary states. This symmetry is further broken into non-stationary states in the thermodynamic limit, which exhibit persistent oscillations. As the driving force increases, the Liouvillian spectrum of these states features a phase transition. Above the transition point, the non-stationary state encodes quantum information, preserving it in a noiseless subsystem. In addition to global loss that affects both bosonic modes identically, we further add global dephasing and show that the oscillating qubit is preserved. Finally, in order to gain additional physical insight, we study the effect of phase perturbation to both modes and observe that likewise they are passively protected, returning approximately to their initial configurations. These results establish dissipative time-crystalline dynamics as a mechanism for passive protection of dynamical quantum information, enabling autonomously stabilized oscillating qubits.