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Multiple Two-qubit Operations Using Semiconductor Coupled Charge Qubits

Two-qubit unitary operations such as controlled rotation (CROT), which rotates the target qubit state conditionally on the control qubit state, and SWAP, which swaps quantum states of the two qubits, are important for performing quantum algorithms and correlating multiple qubits. Using coupled semiconductor charge qubits consisting of two pairs of double quantum dots (DQD), we demonstrated CROT and SWAP, each in a single step. (a) Scanning electron micrograph of the two-qubit device. (b) Coherent oscillations of the first qubit representing the CROT operation. Oscillations (i) and (ii) correspond to cases where the second qubit is in states |1> and |0>, respectively. (c) Data showing additional slow oscillations along the dot-dash line corresponding to correlated coherent oscillations of the first qubit. (d) Correlated coherent oscillations of the first qubit (i). This corresponds to the data along dot-dash line in (c). Oscillation (ii) corresponds to the conditional coherent oscillations along the dot-dash line in (b). (Page 31)

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