Photonic quantum information with time-bins: Principles and applications

TL;DR

This paper reviews the principles, methods, and applications of time-bin encoding in photonic quantum information, emphasizing its robustness for long-distance quantum communication and quantum computing.

Contribution

It provides a comprehensive overview of experimental techniques for preparing, characterizing, and applying time-bin qubits and qudits, including recent advances and challenges.

Findings

Time-bin encoding is highly resilient to environmental perturbations.

Various methods exist for generating and measuring time-bin qubits and entanglement.

Applications include quantum communication, computation, and high-dimensional quantum states.

Abstract

Long-range quantum communication, distributed quantum computing, and sensing applications require robust and reliable ways to encode transmitted quantum information. In this context, time-bin encoding has emerged as a promising candidate due to its resilience to mechanical and thermal perturbations, depolarization from refractive index changes, and birefringence in fiber optic media. Time-bin quantum bits (qubits) can be produced in various ways, and each implementation calls for different considerations regarding design parameters, component compatibility (optical, electrical, electro-optical), and measurement procedures. Here, we provide a comprehensive overview of experimental methods for preparing and characterizing time-bin qubits (TBQs) for quantum communication protocols, with an assessment of their advantages and limitations. We discuss challenges in transmitting TBQs over optical fibers and free-space channels, and methods to overcome them. We also analyze the selection of key time-bin parameters and component requirements across experiments. This leads us to explore the preparation and characterization of time-bin entanglement and examine requirements for interference of time-bins from separate sources. Further, we cover preparation and characterization techniques for high-dimensional time-bin states, namely qudits, and the generation of time-bin entangled qudit pairs. We review time-energy entanglement and key experimental realizations. Finally, we present notable applications of time-bin encoded quantum states, from quantum communication protocols to photonic quantum computation. This work serves as an accessible introduction and a comprehensive review of recent developments.