Acceleration and deceleration of quantum dynamics based on inter-trajectory travel with fast-forward scaling theory

Abstract

Quantum information processing requires fast manipulations of quantum systems in order to overcome dissipative effects. We propose a method to accelerate quantum dynamics and obtain a target state in a shorter time relative to unmodified dynamics, and apply the theory to a system consisting of two linearly coupled qubits. We extend the technique to accelerate quantum adiabatic evolution in order to rapidly generate a desired target state, thereby realizing a shortcut to adiabaticity. Further, we address experimental limitations to the rate of change of control parameters for quantum devices which often limit one's ability to generate a desired target state with high fidelity. We show that an initial state following decelerated dynamics can reach a target state while varying control parameters more slowly, enabling more experimentally feasible driving schemes.

Fast-forward scaling theory

“…FFST also expanded in directions that were not anticipated when Table II was made in 2008, such as protection of quantum state [54], ion sorting [14], generating an excited state from the ground state [26] and non-equilibrium statistical mechanics [22,23]. Problem of the singularity of the driving potential and lack of viable trajectories were mitigated [28,29].…”

“…Do we need another time-and resource-consuming simulations to optimize the control parameters for the slower hardware of Lab B? With this question in mind, deceleration of quantum dynamics was investigated, and they showed the way to find control parameters varying more slowly and still can generate approximately the same end state as the original control of Lab A [29]. This technique can be useful also in the sense that quantum system is typically made to interact with other quantum objects or classical hardwares in quantum technologies.…”

“…It was shown that, in a subset of states that is coupled to background states, a combination of STIRAP and fast-forward driving fields that do not individually generate processes that are competitive with the desired population transfer can generate greater population transfer efficiency than can ordinary STIRAP with similar field strength and/ or pulse duration. More recently, speed control of superconducting qubits, which are attracting attentions in terms of applications to quantum computing, was studied using FFST [29].…”

“…Therefore, modification of the theory is required to resolve this issue. To this end, a novel scheme called inter-trajectory travel (ITT) was developed [29].…”

“…In Ref. [29], the authors found two FF trajectories (see Fig. 4); one starts from the initial state; another ends up the target state at t = T F ; and the two trajectory approach each other at a certain time.…”