Observable Backpropagation for Quantum Simulation Depth
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Solution Overview
Problem
Near-term quantum devices are limited by depth due to hardware noise, making it challenging to execute deep quantum circuits and accurately estimate observable expectation values.
Innovation Solution
The system employs observable backpropagation in combination with state propagation to divide a quantum circuit into two parts, allowing state propagation to be executed on a quantum computer and observable backpropagation to be computed classically, thereby reducing the depth of the quantum simulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the depth of quantum circuit is increased to solve more complex problems, then the computational capability is improved, but the noise and error rate increase making the computation infeasible on near-term devices
Solution Approach 1:
The patent divides a deep quantum circuit into two segments: a shallow quantum circuit that can be executed on near-term quantum devices, and a deep quantum circuit that is simulated classically. This segmentation allows the quantum device to handle only the portion it can reliably execute while the classical computer handles the deeper portion, resolving the contradiction between computational capability and reliability.
2Productivity
If observable backpropagation is applied to the entire quantum circuit, then the effective depth is increased, but the classical computation cost becomes prohibitive
Solution Approach 1:
The patent applies observable backpropagation only to the deep quantum circuit portion that is simulated classically, rather than the entire circuit. This segmentation reduces the classical computation cost while still achieving increased effective depth, as the shallow quantum circuit portion does not require classical backpropagation.
Solution Approach 2:
The patent applies observable backpropagation partially - only to the extent necessary to handle the deep quantum circuit portion. This partial application achieves the benefit of increased effective depth without the prohibitive cost of applying it to the entire circuit, demonstrating the principle of doing just enough to solve the problem.
Data Source
AI summary
One or more systems, devices, computer program products and/or computer-implemented methods of use provided herein relate to observable backpropagation for improving the depth of a quantum simulation. A system can comprise a memory that can store computer-executable components. The system can further comprise a processor that can execute the computer-executable components stored in the memory, wherein the computer-executable components can comprise a quantum computation component that can apply state propagation to a first part of a quantum circuit, on a quantum computer. The computer-executable components can further comprise a classical computation component that can apply observable backpropagation to a second part of the quantum circuit, on a high-performance classical computer.