Researchers demonstrate how to build ‘time-traveling’ quantum sensors

The idea of ​​time travel has fascinated science fiction fans for years. Science tells us that traveling to the future is technically possible, at least if we can travel close to the speed of light, but traveling back in time is impossible. But what if scientists could harness the power of quantum physics to uncover data about complex systems that happened in the past?

A new study suggests that this premise may not be so far-fetched. Published June 27, 2024, Physics Review LetterCater Murch, the Charles M. Hohenberg Professor of Physics and director of the Quantum Leap Center at Washington University in St. Louis, and his colleagues Nicole Junger Halpern of NIST and David Arvidsson-Sukl of the University of Cambridge, are using quantum entanglement to time-Mobile detector.

March describes the concept as similar to sending a telescope back in time and being able to capture a shooting star you see out of the corner of your eye. In the everyday world, the idea is impossible to achieve. But in the mysterious and puzzling world of quantum physics, there may be a way to get around the rules. This is thanks to a property of entangled sensors that March calls “hindsight.”

The process starts with the entanglement of two quantum particles in a quantum singlet state, or in other words, two qubits with opposite spins, so that no matter which way you look, their spins point in opposite directions. From there, one of the qubits, what March calls the “probe,” magnetic field That causes the rotation.

The next step is where the so-called magic happens: if we measure an auxiliary qubit (one that is not used as a probe in the experiment), due to the properties of entanglement, Quantum state (i.e. the spin) “back in time” to the other qubit in the pair, which takes us back to the second step in the process, where the magnetic field rotates the “probe qubit”. This is where the real benefit of hindsight comes into play.

In these types of experiments, which use the rotation of spins to measure the magnitude of a magnetic field, there is usually a one in three chance of the measurement failing. This is because when a magnetic field interacts with a spin, Quantum Bits If you are parallel or anti-parallel to the direction of rotation along the x, y, or z axes, the result will be invalid and there will be no rotation to measure.

Under normal conditions, if the magnetic field is unknown, scientists would have to guess which direction to prepare the spin in, with a one in three chance of failure. The beauty of hindsight is that through time travel, the experimenter can use hindsight to set the best direction for the spin.

Einstein once Quantum entanglement As “spooky action at a distance.” Perhaps the spookiest part about entanglement is that any pair of entangled particles can be thought of as exactly the same particle moving forward and backward in time.

This gives quantum scientists an ingenious new way to build better sensors, especially ones that can effectively go back in time. This kind of sensor could have a variety of uses, from detecting astronomical phenomena to the benefits of studying magnetic fields mentioned above, but many more applications are likely to become prominent as the concept is further developed.