Demonstration of conditional gate operation using superconducting charge qubits.
Following the demonstration of coherent control of the quantum state of a superconducting charge qubit, a variety of qubits based on Josephson junctions have been implemented. Although such solid-state devices are not currently as advanced as microscopic qubits based on nuclear magnetic resonance and ion trap technologies, the potential scalability of the former systems--together with progress in their coherence times and read-out schemes--makes them strong candidates for the building block of a quantum computer. Recently, coherent oscillations and microwave spectroscopy of capacitively coupled superconducting qubits have been reported; the next challenging step towards quantum computation is the realization of logic gates. Here we demonstrate conditional gate operation using a pair of coupled superconducting charge qubits. Using a pulse technique, we prepare different input states and show that their amplitude can be transformed by controlled-NOT (C-NOT) gate operation, although the phase evolution during the gate operation remains to be clarified.
NEC Fundamental Research Laboratories, Tsukuba, Ibaraki 305-8501, Japan. yamamoto@frl.cl.nec.co.jp
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Yamamoto
Yu A
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Pashkin
O
O
Astafiev
Y
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Nakamura
J S
JS
Tsai