Universal quantum gate with hybrid qubits in circuit quantum electrodynamics

Abstract

Hybrid qubits have recently drawn intensive attention in quantum computing. We here propose a method to implement a universal controlled-phase gate of two hybrid qubits via two threedimensional (3D) microwave cavities coupled to a superconducting flux qutrit. For the gate considered here, the control qubit is a microwave photonic qubit (particle-like qubit), whose two logic states are encoded by the vacuum state and the single-photon state of a cavity, while the target qubit is a cat-state qubit (wave-like qubit), whose two logic states are encoded by the two orthogonal cat states of the other cavity. During the gate operation, the qutrit remains in the ground state; therefore decoherence from the qutrit is greatly suppressed. The gate realization is quite simple, because only a single basic operation is employed and neither classical pulse nor measurement is used. Our numerical simulations demonstrate that with current circuit QED technology, this gate can be realized with a high fidelity. The generality of this proposal allows to implement the proposed gate in a wide range of physical systems, such as two 1D or 3D microwave or optical cavities coupled to a natural or artificial three-level atom. Finally, this proposal can be applied to create a novel entangled state between a particle-like photonic qubit and a wave-like cat-state qubit.

Hybrid controlled-sum gate with one superconducting qutrit and one cat-state qutrit and application in hybrid entangled state preparation

“…On the other hand, hybrid gates have attracted tremendous attention recently, because of their importance in connecting quantum information processors with different encoding information-processing units, as well as their significant application in transferring quantum states between a quantum processor and a quantum memory. A number of works on implementing hybrid gates with various qubits, qutrits or qudits have been presented (e.g., [33][34][35][36][37][38][39][40][41][42][43]). However, after a deep search of literature, we note that how to implement hybrid quantum gates with SC qutrits and cat-state qutrits (i.e., qutrits encoded via cat states) has not been studied yet.…”

Single-step implementation of a hybrid controlled-not gate with one superconducting qubit simultaneously controlling multiple target cat-state qubits

“…They play significant roles in connecting quantum information processors with qubits of different encoding and have important applications in the transmission of quantum states between a quantum processor and a quantum memory. Over the past years, based on cavity or circuit QED, theoretical proposals have been presented for implementing a hybrid two-qubit controlled-phase or controlled-NOT gate with a charge qubit and an atomic qubit [64], a charge qubit and a cat-state qubit [65], a photonic qubit and a SC qubit [66], a photonic qubit and a cat-state qubit [67,68], and so on. However, after a deep search of literature, we find that how to implement a hybrid multiqubit quantum gate with SC qubits and cat-state qubits has not been investigated yet.…”

Noise-resistant phase gates with amplitude modulation

“…Since the gate time is inversely proportional to the effective qubitcavity coupling, it can be shortened significantly by employing strong parametric drive. In contrast to previous gate schemes based on the dispersive regime where the desired effective interactions are derived using perturbation theory with large-detuning conditions [17,[37][38][39][40], this proposal enables faster implementation of the phase gates. Besides, we show that the gate robustness against parameter errors, including gate timing error and frequency detuning error, can be increased by shaping the qutrit-cavity coupling strength with time-dependent amplitude modulation.…”