Photonic two-qubit parity gate with tiny cross–Kerr nonlinearity

Coherence stabilization of a two-qubit gate by ac fields.

We consider a CNOT gate operation under the influence of quantum bit-flip noise and demonstrate that ac fields can change the qubit Hamiltonian in such a way that it approximately commutes with the bath coupling. Then the noise effectively acts as phase noise which improves coherence up to several orders of magnitude while the gate operation time remains unchanged. Within a high-frequency appro...

Optimal Realization of a General Two-Qubit Quantum Gate

Since almost all quantum algorithms are represented in the quantum circuit model, the problem of finding a universal set of quantum gates is one the main problems in constructing quantum computers and implementing quantum algorithms. While it is rather easy to find a universal quantum basis, finding basis that satisfies some restrictions, due to implementation requirements, is far more challeng...

Optimal Realization of an Arbitrary Two-Qubit Quantum Gate

Abstract By an explicit construction, we show that an arbitrary two-qubit gate can be implemented by using at most 16 elementary one-qubit gates and 3 CNOT gates. We show that this construction is optimal; in the sense that these numbers of gates is the minimal possible ones. Moreover, we show that if the two-qubit gate belongs to SO(4), then we need only 12 elementary one-qubit gates and 2 CNO...

Two-qubit gates in a microwave photonic quantum computer

Charge qubit driven via the Josephson nonlinearity

We study the novel nonlinear phenomena that emerge in a charge qubit due to the interplay between a strong microwave flux drive and a periodic Josephson potential. We first analyse the system in terms of the linear Landau–Zener–Stückelberg model, and show its inadequacy in a periodic system with several Landau–Zener crossings within a drive period. Experimentally, we probe the quasienergy level...