The time qubit

TL;DR

This paper introduces the concept of a quantum time qubit, where the arrow of time is treated as a superposition, and demonstrates its implementation and implications using interferometry and relativistic quantum mechanics.

Contribution

It proposes a novel framework for a quantum superposition of temporal orientations and links it to relativistic Dirac dynamics, extending quantum clock concepts.

Findings

A superposition of forward and backward time evolution is possible.

Interference experiments can test temporal coherence.

Dirac Hamiltonian couples spin and time qubits, relating matter and antimatter.

Abstract

A spin precessing in a magnetic field is often used as a quantum clock, for example in tunneling-time measurements. We show that such a clock can exist in a coherent superposition of opposite temporal orientations, treating the arrow of time as a quantum two-level system. A Mach-Zehnder interferometer with equal and opposite magnetic fields provides a simple implementation, enabling interference between forward and backward evolution and Bell-type tests of temporal coherence. Extending the framework to relativistic dynamics reveals that the Dirac Hamiltonian describes an intrinsic coupling between a spin qubit and a time qubit, with matter and antimatter corresponding to opposite poles on the temporal Bloch sphere.