Defects and Errors in Quantum Computers Described With New Model
New model helps to describe defects and errors in quantum computers
Points to note…
+ The number of defects that show up in quantum annealing depends on the time taken to pass the phase transition. “If you have millions of years to slowly change the interactions between units, you do not get defects, but that is not very practical,” Mayo remarks. The trick is in designing finite-time—and therefore more practical—schedules to obtain an acceptable number of defects with high probability. The research project in which he participated was aimed at creating a model that could estimate the number of defects and guide the optimum design of these systems.
This annealing of a medium is described by the Kibble-Zurek mechanism, originally designed to explain how a phase transition resulted in ordered structures in the early Universe. It was subsequently discovered that it could be used to describe the transition of liquid helium from a fluid to a superfluid phase. “The mechanism is universal and is also used in quantum computing based on quantum annealing,” explains Mayo. This technology is already on the market and is capable of solving complex puzzles such as the traveling salesman problem. However, a problem with this type of work is that defects that occur during the annealing process will distort the results.
+ To do this, the physicists used theoretical tools to describe phase transitions and numerical simulations to estimate the defect distribution during cooling.
+ As each domain can have one of two values (up or down in the example of the magnetic moments), they could estimate the chances of two opposite domains meeting and creating a defect. This led to a statistical model based on binomial distribution, which could be used to predict how a system should be cooled to create the smallest number of defects. The model was verified against independent numerical simulations and appeared to work well.
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