Efficient Gradient Estimation of Variational Quantum Circuits with Lie Algebraic Symmetries
Stats
変分量子回路のアンサツは一般的に指数関数の形をとる: U(−
→
a ) = eiA(−
→
a )
目的関数L(−
→
a )は観測量Oの期待値として定義される: L(−
→
a ) = tr{OρU(−
→
a )ρU(−
→
a )†}
ハミルトニアンA(−
→
a )がリー代数の次元が多項式オーダーの場合、勾配∇L(−
→
a )を多項式リソースで推定できる
Quotes
"Hybrid quantum-classical optimization and learning strategies are among the most promising approaches to harnessing quantum information or gaining a quantum advantage over classical methods."
"We show that when the dimension of the dynamical Lie algebra is polynomial in the number of qubits, one can estimate the gradient with polynomial classical and quantum resources."
"Turning the gradient estimation to a series of Hadamard tests has another benefit that can further reduce the number of shots to O(log p)."