Simplifying the design of multi-level thermal machines using virtual qubits + Simulating the same physics with two distinct Hamiltonians

Simplifying the design of multi-level thermal machines using virtual qubits + Simulating the same physics with two distinct Hamiltonians

Seminar author:Ayaka Usui

Event date and time:11/11/2021 04:00:pm

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I worked on cold atoms and optical systems to investigate non-classical properties of these systems during my PhD. In this talk, I will present two projects of my work. The first one is a proposal of an approach for studying thermodynamics in qubits, qutrits, or qudits. We consider qubit and higher dimensional machines interfacing with an environment and monitoring a target system. The behaviour of the target is too complicated in general to reveal the dynamics and even the steady state. We suggest to use a virtual qubit as a tool to predict the quantitative behaviour of the target qubit. For this we have generalised the idea of the virtual qubit to higher-level target systems so that one can design autonomous quantum machines beyond a few qubits. The second topic is about proposing a new condition for quantum simulation. If one aims to perform quantum simulation, one usually designs a system such that its Hamiltonian or time evolution operator is the same as the target system. This often requires quantum simulators to be quite complex setups. In this work, we have proposed a way to relax the requirement by not only designing the Hamiltonian but also considering the initial state. As an example, we showed that one-axis twisting, which is the dynamics governed by infinite range interactions, can be simulated by using a nearest-neighbour interaction system (Heisenberg XXX model) with an external field.