A method of determining a state energy

Abstract

There is provided a method for determining an energy level of a physical system using a quantum computer, wherein the energy level of the physical system is described by the summation of a plurality of summands. The method comprises performing an energy estimation routine which comprises preparing an ansatz trial state using an arrangement of quantum gates, wherein the ansatz trial state has a trial state energy dependent on a trial state variable, and estimating an expectation value of each summand respectively. The estimating comprises constructing, based on the arrangement of quantum gates,an initial quantum circuit to operate on the ansatz trial state and further comprises performing a summand expectation value determination sub- routine a plurality of times in an iterative process. The energy estimation routine further comprises summing the expectation value estimates of each summand to determine an estimate for the trial state energy. The method further comprises determining theenergy level of the physical system by applying an optimisation procedure to the energy estimation routine, wherein the optimisation procedure comprises iteratively updating the trial state variableand performing the energy estimation routine a plurality of times to determine a respective trial state energy for each of a plurality of different ansatz trial states.

Description

technical field [0001] The present disclosure relates to quantum computing, and in particular to methods of determining energy levels of physical systems using quantum computers. Background technique [0002] Being able to determine the possible energy states of a physical system such as a molecule or an atom is extremely useful in many technical fields. Determining how the energy might change when the system is perturbed allows for many molecular properties. For example, by electron Schrödinger for many nuclei geometries Equation solving, possibly constructing the potential energy surface (PES) of the molecular system. Knowledge of PES is important, especially in chemistry, as it allows scientists to determine reaction rates, among other things. [0003] Many current methods of obtaining information about the energy states of physical systems rely on classical computers that use complex algorithms to simulate physical systems. However, such methods require significant ...

AI Technical Summary

Problems solved by technology

In practice, the requirement for accuracy means that current quantum computers, and those that could be built in the foreseeable future, simply cannot provide the coherence times that would allow QPE to be performed

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