Rydberg Atom Time Crystals Achieve Multi-Parameter Metrology with Enhanced Sensitivity

The quest for increasingly sensitive measurement techniques drives exploration into novel states of matter and their inherent symmetries. Bang Liu, Jun-Rong Chen, and Yu Ma, alongside colleagues from the University of Science and Technology of China and Harbin Institute of Technology, have investigated enhanced sensing capabilities within the unique framework of dissipative Rydberg atom time crystals. Their research demonstrates a method for multi-parameter metrology, specifically measuring both the frequency and amplitude of microwave fields with unprecedented precision. By meticulously mapping the phase diagram of a driven Rydberg atomic gas, the team identified a critical boundary where time-translation symmetry breaks, enabling enhanced sensitivity beyond conventional limits. This work establishes a promising new approach to precision measurement, grounded in the critical properties of time crystals and opening avenues for advancements in non-equilibrium phase sensing.

Time-Crystal Boundary Enhances Microwave Field Sensing

The pursuit of unprecedented sensitivity in quantum enhanced metrology has driven investigation into non-equilibrium phases of matter and the symmetry breaking they exhibit. Scientists have now demonstrated enhanced sensing capabilities at the boundary of a continuous time-crystal (CTC) phase within a driven Rydberg atomic gas, establishing a new paradigm for precision measurement. The research team mapped the complete phase diagram to pinpoint the parameter-dependent boundary where time-translation symmetry is broken, allowing for the simultaneous measurement of multiple parameters, specifically the frequency and amplitude of a microwave field. Experiments reveal a clear phase transition sequence, beginning with a shift from a thermal phase to a CTC phase, followed by a further transition into a distinct CTC state defined by a different oscillation frequency.

By meticulously examining this transition, the study unveils the precise relationship between the CTC phase boundary and the scanning rate, achieving enhanced precision that surpasses the Standard Quantum Limit. This breakthrough not only establishes a promising approach rooted in the critical properties of time crystals, but also advances a method for multi-parameter sensing in non-equilibrium quantum phases. This work builds upon the understanding that critical points associated with symmetry breaking amplify a system’s response to external stimuli, providing a powerful mechanism for quantum enhanced metrology. The team leveraged this principle by applying minute perturbations to a many-body system at its critical point, where the divergent susceptibility acts as an amplifier, converting microscopic inputs into macroscopic, detectable signals.

Crucially, the research moves beyond single-parameter sensing, addressing the need for simultaneous and correlated measurement of multiple physical quantities, a requirement for many real-world applications. Driven-dissipative ensembles of Rydberg atoms proved to be ideal candidates for this investigation, owing to their long-range interactions and suitability for studying phase transitions and dissipative time crystals. The large dipole moments of Rydberg atoms were exploited as a probe for microwave fields, enabling criticality-enhanced electric field sensing. By merging these distinct applications into a single setup, scientists experimentally realized a Rydberg-based quantum sensor operating within a dissipative time-crystal phase, capable of detecting both microwave frequency and amplitude with significantly improved precision. The team’s measurements of probe transmission versus microwave field amplitude revealed a criticality-enhanced response exhibiting two distinct regimes, corresponding to transitions between thermal, CTC, and further refined CTC phases. This work demonstrates a dramatic enhancement in precision for multi-parameter measurement, exceeding the Standard Quantum Limit by over two orders of magnitude, and opening new avenues for next-generation measurement technologies across diverse fields.

Time-Crystal Boundary Enhances Quantum Sensing Precision

Scientists achieved a significant breakthrough in quantum sensing by demonstrating enhanced precision at the boundary of a continuous time-crystal (CTC) phase within a driven Rydberg atomic gas. The research meticulously mapped the full phase diagram, identifying the precise parameter-dependent phase boundary where time-translation symmetry is broken, enabling the measurement of multiple parameters, specifically microwave frequency and amplitude, within a single experimental setup. Experiments revealed a phase transition from a thermal phase to a CTC phase, followed by a further transition into a distinct CTC state characterized by a different oscillation frequency, demonstrating the system’s complex behaviour under varying conditions. Measurements of probe transmission versus microwave field amplitude uncovered a criticality-enhanced response featuring two distinct criticality regimes, corresponding to the phase transitions between thermal equilibrium, and subsequent CTC phases, each exhibiting unique scaling behaviour and critical slowing down.

The team recorded a dramatic enhancement in precision for multi-parameter measurement of microwave frequency and amplitude, achieving an improvement exceeding two orders of magnitude compared to the thermal equilibrium phase. This performance surpasses the Standard Quantum Limit (SQL), establishing a new paradigm for quantum sensing that leverages the critical properties of non-equilibrium phase transitions. The study focused on a many-body atomic system comprising N atoms with ground state |g⟩ and two nearly degenerate Rydberg states |R1⟩ and |R2⟩, coupled by Rabi frequencies Ω1 and Ω2, and detunings ∆ and ∆ + δ respectively. A microwave field couples the Rydberg states |R1⟩ and |R2⟩ to state |R3⟩ with Rabi frequency ΩMW and detuning ∆MW, described by a Hamiltonian incorporating double Rydberg state model with microwave driving.

Through simulations and experiments, scientists observed that increasing the microwave drive towards a critical value, Ωc MW, gradually prolonged oscillation lifetimes, demonstrating the effect of critical slowing down. Tests prove that near the critical amplitude Ec, decay times diverge, indicating the system’s heightened sensitivity to perturbations and the stabilization of the time-crystal phase. Specifically, the team measured transmission spectra, observing pronounced splitting of transmission resonances into two distinct peaks accompanied by coherent spectral oscillations, signalling the emergence of the time crystal phase at a microwave frequency ranging from 6.405 to 6.605GHz. The breakthrough delivers a pathway for exploiting temporal order in metrological applications, opening possibilities for advanced sensing technologies.