Nobel Prize 2022: The first experiments of the 1970s, 80s, and 90s, which today form the basis of quantum cryptography and quantum computing, were awarded.
John Clauser, Alain Aspect, and Anton Zeilinger receive this year’s Nobel Prize in Physics for research into the fundamentals of quantum information technology, in particular quantum entanglement, on which today’s developments in quantum cryptography and quantum computers are based.
Her work opened the eyes of science to the scope of Erwin Schrödinger’s theoretical discoveries, according to the explanatory statement. The three researchers received the Wolf Prize for Physics in 2010 for the same work.
In 1972, John Clauser first investigated the so-called Bell inequality of quantum physics in experiments with polarized photons and demonstrated the so-called Bell states, which are also known as entangled photons. The measurement results of two experiments with photons at two locations far apart from each other can depend directly on each other, although the type of measurement is chosen at random when the photon arrives and is not fixed from the start.
Two particles behaving as one (Nobel Prize 2022)
The measurement methods were further refined by Aspect and Zeilinger in the 1980s and 1990s in order to rule out errors and falsifications caused by external influences. Because actually there should be no connection between the two measurements. After all, the experiments are so far apart that once the decision has been made as to which measurement to carry out, no information can be transferred between the two measuring points. But if the two photons were previously entangled with each other, the measurement on the second photon gives the opposite result of the first measurement.
This cannot happen when there are two independent photons. Instead, two entangled photons behave like a single physical object made up of two photons and co-existing in two widely separated locations. In physics, it is said that the physical properties of such particles are non-local. Similar behavior has also been observed for a number of other physical particles and quasiparticles, in particular the spin of electrons or the electromagnetic states of superconducting resonant circuits.
Quantum computers are not yet practical
Quantum cryptography takes advantage of the non-local properties of entangled particles to securely encrypt information transmission. Both transmitter and receiver receive part of an entangled pair of photons and measure their properties. The sender uses the information about the entangled pair of photons to encode a bit, allowing the receiver to decode it. Since the quantum states of the individual photons cannot be copied, this part of the message transmission is secured against eavesdropping.
More advanced applications of similar methods, in which the quantum properties of photons or electrons are manipulated in a targeted manner, make it possible to build quantum computers in which multiple qubits are entangled with one another several times, thus physically forming a single object. All parts of this object can be influenced at the same time and thus theoretically enable faster calculations than conventional computers with digital bits. So far, however, no quantum computer has been able to carry out specific calculations that demonstrate this so-called quantum superiority in a practical way.
Anton Zeilinger (Nobel Prize winner), who found out about the selection just an hour before the award ceremony, was able to be interviewed during the award ceremony and said on the phone “I was shocked, but it was a positive shock.” On the other hand, his answer to the question of how he came to the topic can hardly be regarded as realistic advice for people in today’s research world: “Do what you find interesting, don’t worry about applications.”
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