Single spin probe of many-body localization

Abstract

We use an external spin as a dynamical probe of many body localization. The probe spin is coupled to an interacting and disordered environment described by a Heisenberg spin chain in a random field. The spin-chain environment can be tuned between a thermalizing delocalized phase and non-thermalizing localized phase, both in its ground-and high-energy states. We study the decoherence of the probe spin when it couples to the environment prepared in three states: the groundstate, the infinite temperature state and a high energy Néel state. In the non-thermalizing many body localized regime, the coherence shows scaling behaviour in the disorder strength. The long-time dynamics of the probe spin shows a logarithmic dephasing in analogy with the logarithmic growth of entanglement entropy for a bi-partition of a many-body localized system. In summary, we show that decoherence of the probe spin provides clear signatures of many-body localization.

Loschmidt echo in many-body localized phases

“…At the same time, we show that the decay of overlap S(t) itself, contrary to the claims of Ref. 30 does not probe the dephasing dynamics of the MBL phase, but instead gives information about statistics of single particle energies. We also note that the Loschmidt echo was also studied in Ref.…”

“…37 does not probe the dephasing dynamics of the MBL phase, but instead gives information about statistics of single particle energies. We also note that the Loschmidt echo was also studied in Ref.…”

“…If one considers the average overlap S(t) without taking the absolute value, as was done in Ref. 30, one accesses the generating function of the distribution of c i , instead of the dephasing mechanism, as we show in the Appendix A.…”

Nanoscale Quantum Optics

“…Initial experimental results have validated the potential of quantum decoherence microscopy and demonstrated it's applicability to nanoscale sensing [143,144]. Promoting these concepts to real-life applications in life sciences [141] (where for instance ion channels in cell membranes could be investigated) or hard-toaddress open problems in solid-state physics [142,145] (such as studying strongly correlated electron systems) remains an open challenge. However, recent advances in quantum sensing technologies, such as robust, coherent scanning quantum systems [146,147] that employ innovative nanophotonic concepts [148], or the demonstration of nanoscale quantum sensing at cryogenic temperatures [149], render this a highly promising avenue in quantum engineering research.…”

“…Indeed, a quantum sensor in proximity to a sample may experience excess dephasing, which may carry relevant information. Such decoherence microscopy has been proposed in the context of life sciences [141] and fundamental solid-state physics [142]. One key strength of decoherence-based sensing is that it does not require phase-stable signal sources and that quantum control can be used to tailor the spectral response of the quantum sensor to either lock the sensor to a particular sensing frequency or perform noise spectroscopy of the environment [26].…”