Time travel, widely recognized as a staple of science fiction stories and movies, is at least theoretically possible under certain conditions. These include situations such as extremely fast space travel, and the traveler’s proximity to particularly strong gravitational sources.
However, new research suggests that scientists may be getting closer to making the manipulation of time practical, thanks to new innovations in quantum physics.
Einstein’s theory of relativity helped to demonstrate the intimate connection between time and space, revealing that as a traveler’s speed increases while traveling through space, their experience of time slows down. This reality has been experimentally verified in experiments using observed variations on individual clocks that reveal what physicists call time dilation.
Technically, when we walk down the street on any given day of the week, our feet move through time at a slightly different speed than our heads, given the greater proximity of our lower body to the Earth’s gravitational field. However, such variations are so subtle as to be indistinguishable, and such oddities of space and time have little practical significance.
But recent research by a team from Washington University in St. Louis, along with collaborators from NIST and the University of Cambridge, reveals how a new kind of quantum sensor, designed to harness quantum entanglement, could lead to a form of real-life time-traveling detectors. The groundbreaking discovery, detailed in a new study published June 27, 2024, presents a bold possibility: Scientists could soon be able to collect data from the past.
The Strange Realm of Quantum Metrology
In their paper, the team describes experiments with a two-qubit superconducting quantum processor. Their measurements demonstrated a quantum advantage that outperformed any strategy that did not exploit the phenomena of quantum entanglement. The results of their study could make it possible to collect data from the past by exploiting the unique properties of what Einstein called “spooky action at a distance.”
Although impossible in our everyday world, the field of quantum physics offers possibilities that defy conventional rules. Central to this advance is a property of entangled quantum sensors known as “hindsight.”
Kater Murch, a Charles M. Hohenberg professor of physics and director of the Center for Quantum Leaps at Washington University, compares the team’s investigation of these concepts to sending a telescope back in time so it can capture images of a shooting star.
From Qubits to Singlets
In their research, the team devised a process in which two quantum particles become entangled in a quantum singlet state, consisting of a pair of qubits whose opposite spins are always oriented in opposite directions, regardless of their frame of reference. One of the qubits, which the researchers refer to as the “probe,” is then introduced into a magnetic field, which induces rotation.
Meanwhile, the qubit that is not exposed to a magnetic field is measured. This reveals a key aspect of the team’s innovation, as the entanglement properties shared by the two qubits allow the quantum state of the auxiliary qubit to influence the probe qubit under the influence of the magnetic field. The remarkable result is that the probe qubit is influenced retroactively, effectively facilitating the possibility of sending information “back in time.”
This means that scientists are technically able to use this hindsight phenomenon to determine the optimal direction for the probe qubit’s spin in hindsight, almost as if they were looking into the future but controlling the qubit’s behavior in the past. This allows them to increase the accuracy of measurements.
Time-traveling quantum sensors in real life?
Under most circumstances, measuring the spin rotation of a qubit as a means of measuring the magnitude of a magnetic field would have about a one-in-three chance of failure, since the alignment of the field with the direction of the spin effectively throws off the results. In contrast, the hindsight property gave the team the unique ability to retroactively tune the best direction for the spin.
Under these conditions, the entangled particles effectively function as a single entity that exists simultaneously in both forward and backward positions in time. This opens up innovative possibilities for creating advanced quantum sensors that can produce time-manipulated measurements.
The implications of such technology are significant and could help develop new sensor technologies, from detecting rare astronomical phenomena to significantly improving the way researchers study and manipulate the behavior of magnetic fields.
Ultimately, the team’s new “time travel” technology will likely be a major step toward making this well-known science fiction concept a reality, opening up innovative new possibilities and insights into nature that extend beyond our current mastery of time.
The groundbreaking new study by Murch and co-authors Xingrui Song, Flavio Salvati, Chandrashekhar Gaikwad, Nicole Yunger Halpern, and David RM Arvidsson-Shukur, published under the innocent title “Agnostic Phase Estimation,” appeared in Physical assessment letters.
Micah Hanks is the editor-in-chief and co-founder of The Debrief. He can be reached by email at [email protected]Follow his work on micahhanks.com and on X: @MicahHanks.