Viewers of Quantum Events Are Also Subject to Uncertainty

It gets better. What if B is anchored to a quantum object that is in a superposition of two positions? Then the quantum state of A is now smeared out in two different ways depending on the possible location of B. Because determining the quantum state of B determines the state of A, A and B are now entangled.

Renato Rainer, a physicist at the Swiss Federal Institute of Technology in Zurich, believes that a careful consideration of quantum reference frames will solve the paradox of our understanding of the quantum world.

Credit: Giulia Marthaler

In the example above, two subtle properties of quantum systems – superposition and entanglement – ​​depend on the frame of reference. “The key message is that many characteristics that we think are very important, and in a way absolute, are relational” or relative, says Anne-Catherine de la HammetAn author of a recent paper.

Even the sequence of events succumbs to the rigidity of the quantum reference frame. For example, from a reference frame, we can observe the click of a detector occurring at a certain time. But from a different reference frame, the click may end up in a superposition of events occurring before and after some other event. Whether you observe the click as occurring at a specific time or as a superposition of several sequences of events depends on the choice of reference frame.

Stepping Stone to Gravity

Researchers hope to use these changing quantum perspectives to explain the mysterious nature of gravity. Einstein’s general relativity, a classical theory of gravity, states that gravity is the distortion of the fabric of space-time by a massive object. But if the object itself is in a superposition of two positions, how would space-time be perturbed? “It’s very difficult to answer with ordinary quantum physics and gravity,” said Victoria CableBruckner is a researcher in the group and an author of the new paper.

Switch to a reference frame whose origin is in a superposition, though, and the massive object may end up in a fixed location. Now it is possible to calculate its gravitational field. “By finding a convenient quantum reference frame, we can take on a problem we cannot solve [and make it] A problem for which we can only use standard known physics,” Kabel said.

Such perspectives should be useful for analyzing change Future experiments The aim of which is to put the very small population in superposition. For example, physicists Chiara Marletto And Vlatko Vedral Oxford University has Recommended Placing two masses in a superposition of two positions and then studying how this affects their gravitational fields. Increasing efforts to formally describe quantum reference frames can help inform these investigations of the interaction between gravity and quantum theory—an essential step in the theory of quantum gravity.