Quantum measurement reversed by research team
Physicists from the University of Innsbruck say they have developed a way to reverse a quantum measurement – something which should not be possible, according to quantum theory.
The experiment is part of the team's work to develop error correction techniques for future quantum computers.
One of the properties of quantum systems is that measurements are non deterministic – even if the state of a system is known, the outcome of the measurement cannot be determined. A further problem is that taking a measurement alters the system's state.
However, the team has shown that it is indeed possible to reverse a measurement using a quantum error correction protocol. The solution is to transfer the information of one particle onto an entangled state consisting of three particles.
The team contends that if one particle is measured, its original state can be reconstructed from the information residing in the remaining two particles – something which is not forbidden by the laws of quantum mechanics.