Scientists save Schrödinger's cat

One of the predictions of quantum mechanics is that particles behave unpredictably, but a new experiment seems to complicate some of these fundamental ideas.

The researchers were able to predict a type of atomic behavior called quantum leap and even reverse the jump in a new experiment on an artificial atom. Such research could raise larger questions about the nature of physics and could have important implications for the improvement of quantum computers based on the rules of quantum mechanics.

"Our experience shows that there is more to tell in the story" about how quantum mechanics works, student Zlatko Minev, a researcher at IBM's Thomas J. Watson Research Center in Gizmodo, told the student.

The fundamental premise of quantum mechanics is that, at smaller scales, atomic properties are quantized, which means that particles take on discrete rather than continuous states – their properties exist along a staircase rather than a single one. ramp. For example, an electron may be in a lower energy state, but if you add a little more energy, it will not make a slow transition to the new higher energy state. On the contrary, it engages unpredictably in the new state. If you do not look at it, the atom can take intermediate states, but they are not halfway there. The atom would be in both states at the same time, and once you have observed it, it would be immediately caught in one state or another.

But the researchers wondered if they could predict these leaps and prevent them from happening, according to the newspaper. published in Nature.

The artificial team atom is an experimental apparatus consisting of a wire circuit loaded without resistance with a special fence, called Josephson junction, placed in the middle of the wire. In the regular atoms, the "states" are represented by the position of the electron around the nucleus of the atom, but in this artificial atom, the state is represented by a quantized property whose value changes as the electrons move to through the insulating barrier. It is a quantum system (technically a quantum computer with two qubits) and follows the same rules as other quantum systems, including electrons around atoms.

The researchers apply two specially tuned microwave signals. One signal provides the amount of energy needed by the atom to transition between the ground state and the excited state, while the other signal indirectly measures the energy of the circuit during this transition.

The detectors measure a bright flashing photon signal (reflections from the second microwave pulse) when the artificial atom is in the ground state. When their atom is in the excited state, the researchers do not observe flash. Sensitive detectors were able to measure each last photon until the signal went dark, a sign that the transition was about to occur. When the researchers sent another impulse at the right time, they were able to stop and reverse the transition.

You may know Schrödinger's cat. It is a thought experiment in which the life of a cat depends on a two-state quantum process, and according to the rules of quantum mechanics, once the experiment is started, the cat is alive and dead simultaneously. until you open the box. In this case, the living cat is the ground state and the dead cat is excited state. The implication of this research is that scientists can indirectly watch the "cat" move from the living state to the living and dead state simultaneously, and intervene to save the cat.

The other researchers were impressed by the results of the document. "It's an excellent experience," Klaus Mølmer, a professor at the University of Aarhus in Denmark, told Gizmodo. Mølmer pointed out that this does not mean that any quantum process, such as radioactive decay, is canceled and returned to its original state. But he said the researchers carefully point out the limits of their experience.

In this experiment, researchers had been warned only a short time before the transition between states; they can not predict the exact day and time of the transition. But this level of foresight could be useful for quantum computers. Today, computers based on the rules of quantum mechanics are rudimentary and can succumb to random errors. Technology based on this experience could enable quantum scientists to identify errors as they occur. And indeed, some authors of the study work for quantum computing companies; Minev himself holds a permanent research position at IBM.

Much remains to be done before this research is integrated with existing quantum computers. But for now, it's pretty radical to be able to observe the progress of quantum mechanics in real time.