Compound Stabiliser Measurement on Degree-Four Qubit Layouts
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Solution Overview
Problem
Quantum computers with fixed qubit layouts and limited connectivity face challenges in performing fault-tolerant quantum computation due to the difficulty in measuring high-weight stabilisers, which are necessary for logical computations involving more than four qubits, as existing methods require complex operations or hardware modifications.
Innovation Solution
A method for performing compound stabiliser measurements on quantum processing units with uniform degree-four connectivity by scheduling entangling operations between auxiliary qubits and data qubits in a specific interleaved manner to measure large stabilisers without modifying the hardware, using a computer-implemented approach that combines measurement outcomes to correct logical quantum states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If auxiliary qubits are used to measure stabilisers, then error spread is reduced, but qubit connectivity limitations make measuring high-weight stabilisers difficult
Solution Approach 1:
The patent divides the measurement of a single high-weight stabiliser into multiple separate stabiliser components, each measured by a different auxiliary qubit. This segmentation allows the system to work around connectivity limitations by measuring components independently and then combining results classically, rather than requiring all qubits to be simultaneously connected to a single auxiliary qubit.
Solution Approach 2:
The patent introduces classical computing components as intermediaries between the quantum measurement process and the error correction logic. By performing classical combination of measurement outcomes and determination of corrections outside the quantum circuit, the system eliminates the need for complex quantum operations to handle connectivity constraints.
2Device complexity
If qubit connectivity is limited to four qubits, then hardware complexity is reduced, but measuring high-weight stabilisers becomes challenging
Solution Approach 1:
The patent segments the measurement task by associating different stabiliser components with different auxiliary qubits, allowing each component to be measured using only the limited connectivity available between two qubits. The high-weight stabiliser is reconstructed from these segmented measurements through classical processing.
Solution Approach 2:
The patent moves the complex combination logic from the quantum domain to the classical domain. By performing the combination of measurement outcomes and determination of corrections classically, the system adds a computational dimension that compensates for the limited physical connectivity in the quantum hardware.
3Ease of manufacture
If regular fixed qubit arrangements are used, then hardware implementation is simplified, but fault-tolerant quantum computation requires irregular connections and high-weight measurements
Solution Approach 1:
The patent segments the measurement operations into multiple independent stabiliser component measurements that can be performed on the fixed qubit arrangement. Each component uses available connectivity to measure its associated auxiliary qubit, and the results are classically combined to achieve the functionality of measuring high-weight stabilisers that would require irregular connections.
Solution Approach 2:
The patent replaces the need for physical reconfiguration of qubit connections (mechanical change in hardware topology) with a computational approach using classical processing. Instead of modifying the fixed quantum hardware topology to enable high-weight measurements, the system uses classical algorithms to combine results from simpler two-qubit measurements.
Data Source
AI summary
Disclosed herein is a method of performing a compound stabiliser measurement operation in a quantum error correction procedure. The compound stabiliser measurement is performed by combining measurement outcomes associated with stabiliser components. The method allows high-weight stabiliser measurements to be performed on quantum processing units with uniform qubit layouts and degree-four connectivity.