Extending the Variational Quantum Eigensolver to Finite Temperatures
- URL: http://arxiv.org/abs/2208.07621v1
- Date: Tue, 16 Aug 2022 09:14:59 GMT
- Title: Extending the Variational Quantum Eigensolver to Finite Temperatures
- Authors: Johannes Selisko, Maximilian Amsler, Thomas Hammerschmidt, Ralf
Drautz, and Thomas Eckl
- Abstract summary: We present a variational quantum thermalizer (VQT) that extends the variational quantum eigensolver (VQE) to finite temperatures.
We demonstrate the capabilities of qVQT for two different spin systems.
- Score: 0.0
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: We present a variational quantum thermalizer (VQT), called quantum-VQT
(qVQT), which extends the variational quantum eigensolver (VQE) to finite
temperatures. The qVQT makes use of an intermediate measurement between two
variational circuits to encode a density matrix on a quantum device. A
classical optimization provides the thermal state and, simultaneously, all
associated excited states of a quantum mechanical system. We demonstrate the
capabilities of the qVQT for two different spin systems. First, we analyze the
performance of qVQT as a function of the circuit depth and the temperature for
a 1-dimensional Heisenberg chain. Second, we use the excited states to map the
complete, temperature dependent phase diagram of a 2-dimensional J1-J2
Heisenberg model. The numerical experiments demonstrate the efficiency of our
approach, which can be readily applied to study various quantum many-body
systems at finite temperatures on currently available NISQ devices.
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