Improving metrology with quantum scrambling

Abstract

Quantum scrambling describes the spreading of information into many degrees of freedom in quantum systems, such that the information is no longer accessible locally but becomes distributed throughout the system. This idea can explain how quantum systems become classical and acquire a finite temperature, or how in black holes the information about the matter falling in is seemingly erased. We probe the exponential scrambling of a multiparticle system near a bistable point in phase space and utilize it for entanglement-enhanced metrology. A time-reversal protocol is used to observe a simultaneous exponential growth of both the metrological gain and the out-of-time-order correlator, thereby experimentally verifying the relation between quantum metrology and quantum information scrambling. Our results show that rapid scrambling dynamics capable of exponentially fast entanglement generation are useful for practical metrology, resulting in a 6.8(4)-decibel gain beyond the standard quantum limit.

Spectral kissing and its dynamical consequences in the squeeze-driven Kerr oscillator

“…The dynamical consequences of ESQPTs that we presented should also appeal to experimental platforms, where long-range couplings can be tuned to approach models with collective interactions, such as those with cold atoms 72 and trapped ions 73 . Of interest to those experiments is the demonstration of the exponential growth of OTOCs, which we showed to emerge for different initial states placed close to the separatrix that marks the ESQPT.…”

Non-stabilizerness and entanglement from cat-state injection

“…The problem of distinguishing between decoherence and scrambling is of great interest within the community [69,85,86] since any actual experimental implementation in current noisy devices will suffer both from incoherent and coherent errors. Quantum information scrambling, and the OTOC, have already been experimentally investigated in [64,87,88]. We refer the reader to references [62,69] for concrete solutions on how to distinguish between scrambling and noisy dynamics.…”

Fast generation of spin squeezing via resonant spin-boson coupling

“…The limitations arising from curvature can typically be countered by applying the entangling interaction ( ĤTMS in our case) within a time-reversal scheme [9,[25][26][27][28][29][30][31][32][33]. This protocol begins with the same initial state |N/2 z ⟩ ⊗ |0⟩ b and proceeds by letting the TMS interaction act for a time T 1 .…”

“…As in SnT, the exponentially fast enhancement is a consequence of operating the system at the classically unstable point described by ĤTMS . This is a generic feature that can be exploited to implement efficient time-reversal in a diverse set of platforms [9,[25][26][27][28][29][30][31][32][33].…”