Is it possible to express gate u1(λ) through the gates rx, ry, rz while maintaining the phase? Both in principle and in practice (in Qiskit for example)? The single gate rz(λ) is not suitable, because loses phase. And the function transpile (Qiskit) throws an error: "Cannot unroll the circuit to the given basis, ['rx', 'ry', 'rz']. No rule to expand instruction u1" ...
RZ
gate is equal toU1
because the global phase is ignored. So if you docircuit = QuantumCircuit(1); circuit.rz(lambda)
that would implement a u1($\lambda$). $\endgroup$ – Cryoris Jun 18 '20 at 16:05u1
is already the "most basic" gate and cannot be further decomposed. $\endgroup$ – Cryoris Jun 18 '20 at 16:06