Kerr Resonator Switching Rates, with Two-photon Dissipation and Driving, Support Bosonic Quantum Bistability

Quantum computing relies on maintaining the delicate states of qubits, and researchers continually seek ways to improve their stability and performance. V. Yu. Mylnikov, S. O. Potashin, and M. S. Ukhtary, alongside G. S. Sokolovskii, have investigated the switching rates within a specific type of quantum system, a Kerr resonator driven by two-photon interactions. Their work reveals how the rate at which a qubit ‘flips’ between states depends on system parameters, particularly the detuning between driving frequencies, and demonstrates a surprising nonmonotonic relationship. This discovery establishes crucial conditions for optimising the performance of critical cat qubits and offers valuable insights for building scalable quantum computers based on bosonic architectures.

Two-Photon Switching Rate in Kerr Resonators

Researchers analytically investigate switching rates in a Kerr resonator driven by two photons, a system experiencing dissipation and exhibiting quantum bistability. This work focuses on understanding how quickly the system transitions between states, a crucial factor in its performance. The team derives an expression for the switching rate, considering both dissipation and detuning, and demonstrates that increased dissipation slows the switching process. The analysis reveals that the switching rate is sensitive to detuning, displaying a complex, non-monotonic relationship, and identifies specific conditions that maximise the rate. This theoretical framework provides a foundation for optimising Kerr resonator-based switching devices, with implications for quantum information processing and optical communications.

Using Kramers’ theory alongside the P-representation, researchers develop an analytical expression for the bit-flip error rate within the potential-barrier approximation. The results show that, in purely dissipative conditions, the switching rate increases as detuning increases, because the two metastable states move closer together. However, the exponential contribution to the bit-flip rate exhibits a complex dependence on system parameters, extending beyond simple scaling with the average photon number.

Quantum Coherence, Driven Systems, and Circuit QED

This extensive list of references represents a compilation of research related to quantum optics, circuit QED, and the dynamics of systems far from equilibrium. The collection covers a broad range of topics, including qubit control, measurement, and coherence, as well as the impact of noise and dissipation on quantum systems. A central theme is understanding how these factors affect the performance of quantum devices and developing methods to mitigate their effects. The research relies heavily on stochastic methods and master equations to describe the behaviour of open quantum systems, and explores the challenges of quantum measurement and the use of feedback to improve device performance. A strong focus lies on systems that are both driven by external fields and subject to energy loss through dissipation.

Detuning and Nonlinearity Control Qubit Decoherence

This work analytically investigates the switching rate within a two-photon driven Kerr oscillator, a system exhibiting quantum bistability suitable for designing bosonic qubits. Researchers derived an analytical expression for the bit-flip error rate using Kramers’ theory and the P-representation, validating it through comparison with numerical simulations obtained via Liouvillian superoperator diagonalization. The results demonstrate that the switching rate, which governs qubit decoherence, is significantly influenced by the system’s detuning and Kerr nonlinearity.

Specifically, the team found that, in purely dissipative conditions, increasing detuning elevates the switching rate as metastable states converge. However, the exponential contribution to this rate displays a complex relationship with system parameters, extending beyond simple proportionality to the average photon number. Crucially, for systems with substantial Kerr nonlinearity, the switching rate exhibits a non-monotonic dependence on detuning, reaching a minimum at a finite, non-zero value. This arises because detuning’s effect on the potential barrier for switching is dependent on the strength of the nonlinearity, lowering it at low nonlinearity but increasing it beyond a critical point. These findings establish key conditions for optimising the performance of critical cat qubits and are directly relevant to the design of scalable bosonic quantum architectures.