Postdoc @ Institute for Cross-Disciplinary Physics and Complex Systems, IFISC (UIB-CSIC) 

Wednesday June 29 – 12.30 BST

Non-Abelian Quantum Transport and Thermosqueezing Effects 

Nonequilibrium classical systems support the transport of particles (e.g., electrons) and heat. Combining these two currents can lead to interesting physical applications, known as thermoelectricity. These include the Seebeck and Peltier effects, which are used in several electronic devices. Some examples are thermocouples and thermopiles useful for measuring temperature, or thermoelectric generators, used for recycling waste heat in power plants and automobiles. Quantum systems, in addition to heat and particles, support the transport of other types of excitations, with more exotic properties. These include magnetization currents, or radiation squeezing, a widely used property in quantum technologies with roots in the uncertainty principle. 
By combining heat and squeezing currents, we derive a set of thermosqueezing effects, completely analogous to the thermoelectric case [1].  Our key insight is to use generalized Gibbs ensembles with noncommuting charges as the basic building blocks and strict charge-preserving unitaries in a collisional setup, building from previous considerations on squeezed thermal reservoirs [2]. These effects may have applications for new sensing technologies and for heat-to-work conversion in the quantum regime. Furthermore, an entire theoretical formalism for studying the joint transport of currents associated with observables that do not commute at the quantum level (the so-called non-Abelian charges) is formulated. This framework develops on the theory of linear transport processes, put forth by Onsager almost nine decades ago, and extends it to more general kinds of quantum processes. Remarkably, it is demonstrated that, within this framework, quantum coherence in the form of noncommutativity can lead to a reduction in dissipation. Therefore, the results presented here open new avenues for the thermodynamic description and exploitation of quantum effects. 

[1] Gonzalo Manzano, Juan M.R. Parrondo, and Gabriel T. Landi, PRX Quantum 3, 010304 (2022). 
[2] Gonzalo Manzano, Phys. Rev. E 98, 042123 (2018).