Scientists have demonstrated a new type of quantum sensor that uses quantum entanglement to make measurements that seemingly “travel back in time.” The research, led by Kater Murch from Washington University in St. Louis and collaborators from NIST and the University of Cambridge, was published in Physical Review Letters on June 27, 2024. The process involves entangling two quantum particles, or qubits, in a quantum singlet state where their spins point in opposite directions.
One qubit, called the “probe,” is exposed to a magnetic field that causes it to rotate. When the other qubit, the “ancilla,” is measured, its state is sent back in time to influence the probe qubit. This property, which Murch calls “hindsight,” allows the researchers to retroactively set the best direction for the spin of the probe qubit.
Normally, measuring the rotation of a qubit’s spin to determine a magnetic field has a one-in-three chance of failure if the field aligns with the spin direction.
Quantum sensor ‘hindsight’ effect explained
However, the entanglement enables the quantum state of the ancilla qubit to affect the probe qubit in the past, increasing measurement accuracy.
The entangled particle pair can be considered a single entity that exists both forward and backward in time. This enables the development of advanced quantum sensors capable of making temporally manipulated measurements. The implications of this breakthrough are significant, from detecting rare astronomical phenomena to studying magnetic fields with improved precision.
The “time travel” technology represents a step toward turning the science fiction concept into reality, offering new possibilities and insights into the nature of time. While the findings present an innovative approach to quantum sensing, the researchers acknowledge the need for further research, the current limitations in scalability, and the requirement for highly controlled environments. Nevertheless, the study provides a significant advance in understanding quantum entanglement and its potential applications.
