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Early Stage Researcher 5, AALTO, FINLAND


Project title and work package:

Quantum heat engines and refrigerators in mesoscopic circuits, work package Quantum thermodynamics




Heat engines using coherent quantum systems, such as superconducting circuits, as working substance are of considerable interest currently. Yet realisations of the theoretical concepts of such machines are still lacking. You are to work on heat engines based on known superconducting qubit technology, now being harnessed at AALTO for thermodynamics experiments. An archetypal device is the so-called quantum Otto engine, where the four-stroke cycle consists of adiabatic expansion, rejection of heat at constant volume, adiabatic compression, and heat extraction at constant volume. This cycle can be realised by employing two non-identical LCR-resonators coupled to a qubit whose level spacing (« volume ») is varied by magnetic flux. The resistors of the LCR-resonators serve as the cold and hot bath of the Otto engine, and their temperatures are monitored by tunnel junction probes. Your work consists of design, realisation and measurement of such heat engines. In the first place, you are expected to use a superconducting qubit as a heat switch between baths coupled through it only at their resonance frequency. Following this DC experiment, the focus will be on RF-cycles of the qubit realizing a four-stroke quantum engine/refrigerator. One of the key questions to be addressed is whether quantum coherence can be used into the benefit in terms of power and efficiency of a heat engine. 


Expected Results:

- Quantum heat switch based on a superconducting qubit realised experimentally.

- Cooling of a mesoscopic bath by an Otto refrigerator based on a superconducting transmon qubit.

- Influence of coherence and entanglement on the performance of quantum refrigerators studied experimentally.


Planned secondments:

at CTH, Sweden (1 month, Year 1) to get trained on superconducting resonators, at CNRS, France (1 month, Year 2) to get trained in some aspects of theory of photon heat transport, at ASQELLA, Finland (2 months, Year 3) to get trained on nanofabrication of THz detectors and related read-out techniques.




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