Enhanced precision bound of low-temperature quantum thermometry via dynamical control

Abstract

We consider a thermometer modelled by a dynamically-controlled multilevel quantum probe in contact with a bath. Dynamical control in the form of periodic modulation of the energy-level spacings of the quantum probe enables us to dramatically increase the accuracy of temperature estimation at low temperatures, by maximizing the relevant quantum Fisher information. As opposed to the diverging relative error at low temperatures obtained in conventional thermometers, periodic modulation of the probe enables high-precision thermometry close to the absolute zero, with a constant (temperature-independent) relative error bound. Alternatively, such control may allow for high-precision measurement of a broad range of temperatures. The proposed approach may find diverse applications related to precise probing of the temperatures of many-body quantum systems in condensed matter and ultracold gases, as well as in different branches of quantum metrology beyond thermometry, for example in precise probing of different Hamiltonian parameters in many-body quantum critical systems.

Measuring the temperature of cold many-body quantum systems

“…Luckily, however, the sensitivity of a probe with a finite and fixed energy gap may be substantially increased at arbitrarily low temperatures by driving it periodically [26]. This would open dissipative decay channels at frequencies corresponding to the "Floquet harmonics" of the dynamically controlled system [39].…”

“…Our findings imply that engineering the probe-sample coupling to guarantee a good thermal contact with the lowfrequency modes is the key to precise low-temperature quantum thermometry. In this sense, reservoir engineering and dynamical control [26] could come to play a major role in prac- appear depicted in orange and red, respectively. Although not shown, the nodes (gray dots) of the lattice are are connected by short-ranged interactions.…”

Dynamical approach to ancilla-assisted quantum thermometry

“…If the probe is small, this has the advantage of inducing a negligible disturbance to the thermal equilibrium of the reservoir. The same principle applies in the quantum regime and substantial interest has recently been devoted to the design and properties of sensitive quantum thermometers [1][2][3][4][5][6][7][8][9].…”

Quantized refrigerator for an atomic cloud

“…(iv) The temperature of each bath has to be measured independently through in-situ measurements of the bath profile and density correlations [43][44][45]. Another intriguing approach would be to employ an impurity as a local thermometer [38,[46][47][48], provided the thermalization between the bath and the WM is well at hand [49].…”