Observers of quantum phenomena are also subject to uncertainty

It gets better. But what if B is also bound to a quantum object in a superposition of two places? Then the quantum state of A is now tainted in two different ways depending on the possible locations of B. Since determining the quantum state of B determines the state of A, A and B are now entangled.

Physicist Renato Renner of the Swiss Federal Institute of Technology believes that careful consideration of quantum reference frames will resolve paradoxes in our understanding of the quantum world.

Credit: Giulia Marthaler

In the above example, the two quintessential properties of quantum systems – superposition and entanglement – depend on the reference frame. “The main message is that many properties that we consider very important and in some sense absolute are relational,” or relative. Anne-Catherine de la Hametteco-author of the final paper.

Even the sequence of events obeys the rigidity of quantum reference frames. For example, we can observe the clicking of a detector occurring at a certain time from a reference frame. However, due to a different frame of reference, a click may result in a superposition that occurs before and after another event. Whether you observe the click as occurring at a specific time or as a superposition of different sequences of events depends on the choice of reference frame.

Gravity stepping stone

Researchers hope to use these changing quantum perspectives to make sense of the puzzling nature of gravity. Einstein’s theory of general relativity, the classical theory of gravity, says that gravity is the bending of the fabric of space-time by a massive object. But if the object itself is in the superposition of two places, how will space-time bend? “It’s very difficult to answer with ordinary quantum physics and gravity,” he said Victoria CableHe is a researcher in Bruckner’s group and a co-author of the new paper.

However, switch to a reference frame whose origin is in superposition, and the massive object may end up in a specific location. Now it becomes possible to calculate its gravitational field. “By finding a comfortable quantum reference frame, we can take a problem that we can’t (and can’t) solve using standard known physics,” Cable said.

Such perspective should be useful for analyzing changes future experiences This aims to place extremely small masses in superpositions. For example, physicists Chiara Marletto and Vlatko Vedral There is Oxford University he suggested putting each of the two masses in a superposition of the two places and then studying how this affects their gravitational fields. Increasing efforts to formally describe quantum reference frames may help to understand these studies of the interplay between gravity and quantum theory—an important step for quantum gravity theory.