# Deterministic quantum state transfer between remote qubits in cavities

## TL;DR

This paper compares wave packet shaping and adiabatic passage protocols for quantum state transfer between distant cavity-embedded qubits, showing that adiabatic passage can better mitigate cavity losses under certain conditions.

## Contribution

It provides a comprehensive analysis of two state transfer protocols, revealing conditions where adiabatic passage outperforms wave packet shaping in lossy environments.

## Key findings

- Adiabatic passage mitigates cavity losses more effectively than wave packet shaping.
- Photon arrival probability is limited by a trade-off between non-adiabaticity and off-resonant mode coupling.
- Neither protocol can fully overcome transmission losses, emphasizing the importance of cavity parameter optimization.

## Abstract

Performing a faithful transfer of an unknown quantum state is a key challenge for enabling quantum networks. The realization of networks with a small number of quantum links is now actively pursued, which calls for an assessment of different state transfer methods to guide future design decisions. Here, we theoretically investigate quantum state transfer between two distant qubits, each in a cavity, connected by a waveguide, e.g., an optical fiber. We evaluate the achievable success probabilities of state transfer for two different protocols: standard wave packet shaping and adiabatic passage. The main loss sources are transmission losses in the waveguide and absorption losses in the cavities. While special cases studied in the literature indicate that adiabatic passages may be beneficial in this context, it remained an open question under which conditions this is the case and whether their use will be advantageous in practice. We answer these questions by providing a full analysis, showing that state transfer by adiabatic passage -- in contrast to wave packet shaping -- can mitigate the effects of undesired cavity losses, far beyond the regime of coupling to a single waveguide mode and the regime of lossless waveguides, as was proposed so far. Furthermore, we show that the photon arrival probability is in fact bounded in a trade-off between losses due to non-adiabaticity and due to coupling to off-resonant waveguide modes. We clarify that neither protocol can avoid transmission losses and discuss how the cavity parameters should be chosen to achieve an optimal state transfer.