Quantum Verification Apparatus Qubit Segmentation
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Solution Overview
Problem
Current quantum computer verification methods require a large number of copies, which increases exponentially with the size of the quantum computer, making it inefficient and time-consuming to verify the correctness of large-scale quantum computers.
Innovation Solution
A quantum computer verification apparatus and method that divides the qubits into two sets to reduce the number of CZ gates across them, allowing for efficient estimation of fidelity using a reduced number of samples, specifically O(2^{12}Dϵ^6(D+log(1/δ)/ϵ^4)^3) samples for an n-qubit state with density D=O(log n).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional verification method is used, then verification can be performed for any quantum chip, but the number of copies required increases exponentially with the size of the quantum computer
Solution Approach 1:
The patent divides the n qubits into two separate groups (first group and second group), allowing the verification process to be segmented into independent measurements on each group. This segmentation reduces the exponential complexity by transforming the problem from verifying the entire n-qubit state to verifying two smaller groups separately, thereby reducing the number of copies required from exponential in n to exponential in a smaller effective size.
2Productivity
If the quantum computer size n is increased to exhibit practical superiority, then calculation speed improves, but verification time increases exponentially
Solution Approach 1:
By segmenting the quantum computer into two groups of qubits and performing separate measurements, the verification time is reduced from exponential in n to exponential in a smaller effective size. This allows large-scale quantum computers to maintain their calculation speed advantage while having their verification time reduced to a manageable level.
3Measurement precision
If more copies are used to improve estimation accuracy, then fidelity estimation precision improves, but the time and resources required increase exponentially
Solution Approach 1:
The patent segments the fidelity estimation process into independent measurements on two separate qubit groups. This allows the estimation precision to be maintained while reducing the total number of copies required, as each group can be measured independently with fewer copies than would be needed for the full n-qubit system.
Solution Approach 2:
The patent performs measurements on subsets of qubits (first group and second group separately) rather than requiring full n-qubit measurements. This partial action approach achieves sufficient fidelity estimation precision by focusing measurements on critical subsets, thereby reducing the excessive resource requirements of conventional methods.
Data Source
AI summary
A quantum computer verification apparatus includes: a division unit 1 that divides n qubits on which a quantum circuit U acts into m qubits and (n−m) qubits such that the number of CZ gates across the qubits becomes D=O(log n); a stabilizer operator calculation unit 2 that calculates a stabilizer operator {circumflex over ( )}sk for each k; an estimation unit 3 that randomly selects (i, j, i′, j′) T2 times for each k and calculates estimates of a real part of a value of the following expression to obtain T2 estimates;(-1)i·j+i′·j′Tr[ρout[Qi,j†(∏i=1nZiki)Qi′,j′]]an average calculation unit 4 that obtains an average of the T2 estimate for each k and sets the obtained average as an estimate of Tr[ρout{circumflex over ( )}sk] corresponding to each k, and a fidelity estimation value calculation unit 5 that obtains an average of estimates of Tr[ρout{circumflex over ( )}sk] corresponding to each k.