Unconventional quantum annealing in many-body open quantum systems

Quantum computers promise significant advantages in solving complex problems currently intractable for classical computers by leveraging principles of quantum physics such as superposition, entanglement, and tunneling to perform operations on data. One well-known approach to quantum computation is quantum annealing, pioneered by D-Wave Systems Inc., which develops quantum annealing processors to tackle optimization and sampling problems. Recently, D-Wave has advanced its capabilities to perform coherent annealing within short periods of time constrained by the interaction between the processor and the thermal environment. This limited time may not be sufficient to achieve low-energy solutions in a single forward annealing process. In this project, we try to mitigate this shortcoming by iterative or cyclic quantum annealing protocol, a combination of forward and reverse annealings to reduce the residual energy in each cycle. A crucial aspect of this protocol is that coherence within the system is required primarily during a single cycle. Between cycles, the system remains in a deeply glassy phase, where the qubits are frozen. Consequently, cycles can be repeated well beyond the thermal relaxation time without substantial thermal excitation. We use and develop iterative evolution methods with and without biases: the former linked to bang-bang protocol and continuous-time quantum walk, the latter to iterative quantum optimization. We also utilize advanced computational techniques, including tensor network methods and entanglement measures, to further investigate such an open quantum many-body system. This project aims to benefit D-Wave by developing new quantum algorithms that enhance the performance and efficiency of its quantum processors.

Faculty Supervisor:

Igor Herbut

Student:

Partner:

D-Wave Systems Inc.

Discipline:

Physics

Sector:

Manufacturing; Professional, scientific and technical services

University:

Simon Fraser University

Program: