Quantum bus

A quantum bus is a device which can be used to store or transfer information between independent qubits in a quantum computer, or combine two qubits into a superposition. It is the quantum analog of a classical bus. There are several physical systems that can be used to realize a quantum bus, including trapped ions, photons, and superconducting qubits. Trapped ions, for example, can use the quantized motion of ions (phonons) as a quantum bus, while photons can act as a carrier of quantum information by utilizing the increased interaction strength provided by cavity quantum electrodynamics. Circuit quantum electrodynamics, which uses superconducting qubits coupled to a microwave cavity on a chip, is another example of a quantum bus that has been successfully demonstrated in experiments.^[1]

History

The concept was first demonstrated by researchers at Yale University and the National Institute of Standards and Technology (NIST) in 2007.^[1][2][3] Prior to this experimental demonstration, the quantum bus had been described by scientists at NIST as one of the possible cornerstone building blocks in quantum computing architectures.^[4][5]

Mathematical description

A quantum bus for superconducting qubits can be built with a resonance cavity. The hamiltonian for a system with qubit A, qubit B, and the resonance cavity or quantum bus connecting the two is [math]\displaystyle{ \hat{H}=\hat{H}_r+\sum\limits_{j=A,B} \hat{H}_j +\sum\limits_{j=A,B}hg_i\left(\hat{a}^\dagger\hat{\sigma}^j_-+\hat{a}\hat{\sigma}^j_{\text{+}}\right) }[/math] where [math]\displaystyle{ \hat{H}_j = \frac{1}{2}\hbar\omega_j\hat{\sigma}^j_+\hat{\sigma}^j_- }[/math] is the single qubit hamiltonian, [math]\displaystyle{ \hat{\sigma}^j_+\hat{\sigma}^j_- }[/math] is the raising or lowering operator for creating or destroying excitations in the [math]\displaystyle{ j }[/math]th qubit, and [math]\displaystyle{ \hbar\omega_j }[/math] is controlled by the amplitude of the D.C. and radio frequency flux bias.^[6]

References

0.00 (0 votes) Original source: https://en.wikipedia.org/wiki/Quantum bus. Read more