Manipulating qubits

Lajos Diósi

Lajos Diósi

Hengkui Wu, Weiguo Zhu, Jinhao Pang +1 more

Abstract Quantum computing is an emerging technology which will influence the future. Quantum computing is currently limited by the scalability of qubits, especially the qubits manipulation of superconducting computing. In this paper, a superconducting qubits manipulation method based on AWG (Arbitrary Waveform Generator) is proposed. Based on the superconducting quantum computing system, the overall scheme of qubits manipulation is presented, including overall framework, multichannel coherent arbitrary waveform generation design, quantum state reading and acquisition design, multichannel synchronization design and quick feedback transceiver design. The simulation and experiment results show that the proposed method has good scalability, high synchronization index and good signal quality, which can meet the requirements of superconducting quantum computing for qubits manipulation.

Ming Zhang

For a multiple qubit system, the dimension of the system is exponentially large in the number of qubits, one may ask whether the cost of manipulating multiple qubit systems is exponentially large in the number of qubits or not? It has been found that only n(n + 3)/2 control Hamilton will guarantee open-loop controllability of n-qubit systems when only single qubit operators and two-qubit-interactive operators are permitted. Further more, the minimum cost of deterministically generating multiple-qubit GHZ entangled state will be at most linearly large in the number of qubits. To some extent, one may predict that the "cost" of manipulating multiple-qubit systems is tolerable.

Mathias S. Scheurer, Alexander Shnirman

We investigate the nonadiabatic processes occurring during the manipulations of Majorana qubits in one-dimensional semiconducting wires with proximity-induced superconductivity. Majorana qubits are usually protected by the excitation gap. Yet, manipulations performed at a finite pace can introduce both decoherence and renormalization effects. Although exponentially small for slow manipulations, these effects are important as they may constitute the ultimate decoherence mechanism. Moreover, as adiabatic topological manipulations fail to produce a universal set of quantum gates, nonadiabatic manipulations might be necessary to perform quantum computation.