Undergraduate @ Institute Néel 

Tuesday June 28 – 17.15 BST

The thermodynamic cost of quantum measurements in the circuit quantum electrodynamics architecture

Since work can be extracted from coherences in the eigenenergy basis [1], conversely, measuring a state in this basis can have a cost. Theoretically, this cost is proportional to the QC-mutual information obtained from the measurement~[2], but this bound is not always reachable in the experimental context. Since some resources, such as thermal states, are much easier to produce than others, one could wonder about their measuring capabilities. Here, in a circuit quantum electrodynamics setup, we investigate the resources required to perform quantum measurements of a qubit. We compare the measurement backaction and signal-to-noise ratio of single-photon, coherent and thermal fields. We find that in the strong dispersive limit the thermal light is capable of performing quantum measurements with comparable figure of merit to coherent light. Furthermore, we analyze the energetic and entropic costs of these quantum measurements at different measurement strengths and investigate the fundamental reasons behind these experimental results. This work demonstrates a new, efficient approach to quantum measurements in circuit quantum electrodynamics and provides a new point of view to the energetic cost of a measurement. 
[1] P. Kammerlander, J. Anders, “Coherence and measurement in quantum thermodynamics”, Scientific Reports 6, (2016). 
[2] T. Sagawa, M. Ueda, “Minimal Energy Cost for Thermodynamic Information Processing: Measurement and Information Erasure”, Phys. Rev. Let. 102. (2009). 
*This work was supported by the John Templeton Foundation, Grant No. 61835 

Categories: Talks Tuesday June 28