Superposition of causal order as a metrological resource for quantum thermometry

Understand

We propose a novel approach to qubit thermometry using a quantum switch, that introduces an indefinite causal order in the probe-bath interaction, to significantly enhance the thermometric precision.

• The resulting qubit probe shows improved precision in both low and high temperature regimes when compared to optimal qubit probes studied previously.
• It even performs better than a Harmonic oscillator probe, in spite of having only two energy levels rather than an infinite number of energy levels as that in a harmonic oscillator.
• We thereby show unambiguously that quantum resources such as the quantum switch can significantly improve equilibrium thermometry.