Abstract
A goal of quantum information technology is to control the quantum state of a system, including its preparation, manipulation, and measurement. However, scalability to many qubits and controlled con-nectivity between any selected qubits are two of the major stumbling blocks to achieve quantum com-puting (QC). Here we propose an experimental method, using Josephson charge qubits, to efficiently solve these two central problems. The proposed QC architecture is scalable since any two charge qubits can be effectively coupled by an experimentally accessible inductance. More importantly, we formulate an efficient and realizable QC scheme that requires only one (instead of two or more) two-bit operation to implement conditional gates.
Highlights
The charge qubit is achieved in a Cooper-pair box [2], where two dominant charge states are coupled through coherent Cooper-pair tunneling [3], while the phase qubit is based on two different flux states in a small superconducting-quantum-interference-device (SQUID) loop [4,5]
Coherent oscillations were demonstrated in a Josephson charge device prepared in a superposition of two charge states [2]
These striking experimental observations reveal that the Josephson charge and phase devices are suitable for solid-state qubits in quantum information processing
Summary
We focus on the Josephson charge qubit realized in a Cooper-pair box and propose a new quantum-computing (QC) scheme based on scalable charge-qubit structures. A scalable way of coupling Josephson charge qubits was proposed [1,3] in terms of the oscillator modes in an LC circuit formed by an inductance and the qubit capacitors. In this design, the interbit coupling is switchable and any two charge qubits can be coupled. For the kth Cooper-pair box, a superconducting island with charge Qk 2enk is weakly coupled by two symmetric dc SQUIDs and biased by an
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