Efficient Control of Qubits Interaction Explored Through Frequency-Regulated Signals

The article discusses the importance of controlled interaction between qubits and the logical elements of quantum devices. It explores new methods of organizing qubit interaction with microwave fields of resonators, focusing on the impact of frequency-regulated radio frequency signals on a superconducting Josephson qubit.

The article also examines the influence of the Kerr environment on qubit entanglement and uses the quantum Liouville equation to analyze system dynamics. Numerical simulations reveal that Kerr nonlinearity reduces maximum qubit entanglement for separable initial states but can create long-lived entangled states for entangled initial states. The study identifies optimal conditions for effective qubit control and management.

What is the Importance of Controlled Interaction Between Qubits?

The article begins by emphasizing the necessity of implementing controlled interaction between qubits, which are the logical elements of quantum devices such as quantum computers and quantum networks. Alongside traditional methods, the development of new, more efficient ways of organizing the interaction of qubits with microwave fields of resonators used for generating and controlling the entanglement of qubits is required. One proposed method is based on the impact of frequency-regulated radio frequency signals on a superconducting Josephson qubit connected by a large Josephson junction with a free qubit.

How Does the Kerr Environment Influence Qubits?

The article then delves into the influence of the Kerr environment of a resonator, in which one of the two qubits is placed, on their entanglement induced by a coherent or thermal frequency-regulated radio frequency field of the resonator. The quantum Liouville equation for the full-density matrix was examined to analyze the system’s dynamics under consideration. An exact solution to this equation was found for initial separable and entangled states of qubits. This same solution of the evolution equation was used to calculate the criterion of entanglement of qubits – coherence.

What are the Results of Numerical Simulation?

Numerical simulation of coherence was conducted for various states of qubits, coherent and thermal fields of the resonator, as well as different values of the intensity of the resonator field and the parameter of Kerr nonlinearity. The results showed that for separable initial states of qubits, the inclusion of Kerr nonlinearity reduces the maximum degree of entanglement of qubits. For an entangled initial state of qubits, the possibility of creating long-lived entangled states in the presence of Kerr nonlinearity was demonstrated.

What are the Conclusions Drawn from the Study?

The study concluded by identifying the type of initial states of qubits and the range of values of resonator field intensities and the parameter of Kerr nonlinearity for which the most effective control and management of the evolution of qubits, as well as the degree of their entanglement in the physical system under consideration, is possible.

What are the Key Terms in the Study?

The study’s key terms include superconducting charge qubits, quantum microwave field, coherent state, Kerr nonlinearity, coherence, and long-lived entangled states. These terms are crucial in understanding the complex dynamics of qubits and their interaction with the Kerr environment.