Reversing Quantum MeasurementsCategory: Science & Technology
Posted: February 20, 2013 08:01AM
The laws of thermodynamics affect every process that goes on among us and the second law is perhaps the best example of this. According to that law, no process that would decrease the entropy of a system may occur, which basically translates to most processes occur in only one direction. It is still possible to reverse a process, but doing so is itself another process which cannot decrease the entropy of the Universe. Now researchers at the University of Innsbruck have found a way to reverse a quantum measurement, which is typically impossible.
Quantum mechanics is very odd in part because one of its properties is that it is non-deterministic, which means that even if you know all of the information about a system, you cannot predict the outcome of a measurement of the system. The act of making a measurement also changes the system irreversibly, but, as the researchers have discovered, it is still possible to reverse the system using another process. In this case they did so by entangling the state of one particle with three others. This allowed them to measure one particle and by using a quantum error correction technique with the information of the other particles, the state of that first particle, pre-measurement, can be determined.
Exactly what may come of this research is hard to say, but it will likely have an impact on quantum computers of the future, if only because it was performed on a prototype quantum information processor. My best guess is that this method may be used to make stronger error correction systems for future quantum computers.
Source: University of Innsbruck