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- If you don't open it, you won't understand: How the new Schrodinger's cat works
If you don't open it, you won't understand: How the new Schrodinger's cat works
Schrodinger's famous cat, which has become a symbol of quantum physics, has received an unexpected sequel in real science. Scientists from the University of Oxford have introduced a new type of superposition, which makes it possible to form more complex states than before. According to the researchers, this development can help in the creation of more stable quantum computers and the development of quantum technologies. Why the discovery aroused the interest of the scientific community and when it will be able to find practical application — in the material of Izvestia.
What exactly did the Oxford physicists manage to do?
Quantum superposition is one of the key phenomena of quantum physics. It is based on the idea that a quantum object can be in several states at the same time. This is exactly what underlies the thought experiment with Schrodinger's cat, which is considered both alive and dead until the moment of measurement.
Quantum computing works on the same principle: the basic element of a quantum computer, a qubit, can simultaneously be in states 0 and 1. However, physicists from the University of Oxford were able to go beyond standard circuits and learned how to create much more complex quantum superpositions.
Alexey Rubtsov, head of the Correlated Quantum Systems research group at the Russian Quantum Center, explains that the experiment uses an ultracold ion trapped in a Paul trap. Its quantum behavior is determined by two degrees of freedom: an external motion, which can be described as a harmonic oscillator, and an internal state, which for simplicity is called spin.
The Paul ion trap is a device that uses alternating electric fields to keep charged particles practically stationary and isolate them from external influences.
— First, the researchers create a superposition of the two internal states of the ion. Then, for each component of this superposition, different quantum states of the oscillator are independently formed. After that, both branches are coherently combined again," the expert explains.
In fact, scientists have learned how to control two levels of a quantum system simultaneously and "separate" them along different quantum trajectories, and then reconnect them into a single state. This allows us to construct much more complex superpositions than in previous experiments.
Natalia Maleeva, director of the NUST MISIS Quantum Design Center, emphasizes that the importance of the work is related not only to the specific result, but also to the expansion of the possibilities of managing quantum states in general.
— Theoretically, we can use this approach not only with two coherent states directed diametrically to each other, but also with three and four. This is possible, but it is difficult to practically implement such an interaction between several wave packets," the expert explains.
In this regard, the researchers not only received a new version of the "Schrodinger's cat", but also expanded the set of quantum states available for a real experiment. This is what makes the work significant for the further development of quantum technologies.
How it will improve quantum computers
Quantum computers are capable of solving tasks that remain too complex or require huge computing resources for modern supercomputers. First of all, we are talking about modeling molecules and materials, developing new drugs, optimizing complex logistics systems and other calculations where it is necessary to simultaneously analyze a huge number of options.
One of the main obstacles to creating powerful quantum computers is mistakes. Quantum information is very fragile: accidental exposure to the environment can disrupt the state of the qubit and cause calculations to fail. Therefore, scientists around the world are looking for ways to make quantum systems more stable.
As Evgeny Polyakov, PhD, Associate Professor at the National Research Nuclear University MEPhI, explains in an interview with Izvestia, the existence of quantum states is confirmed by interference, a characteristic pattern that occurs when quantum states overlap each other. It was precisely such interference patterns that the Oxford researchers observed, proving that the complex superpositions they created really exist.
Quantum computing works on the same principle. According to the expert, a quantum computer simultaneously operates with a variety of solutions to a problem, and then, due to interference, the correct answers are amplified and the incorrect ones are suppressed.
— By controlling the shape of such "clouds", it is possible to solve tasks that are impossible for conventional computers, but this feature makes quantum systems extremely vulnerable. Any external influence can disrupt the state of the qubit and lead to loss of information. Therefore, one of the main tasks of developers remains to create effective mechanisms for detecting and correcting errors," Polyakov notes.
According to Polyakov, the Oxford paper does not offer a ready-made solution to this problem, but creates a new foundation for it. While in the traditional "Schrodinger's cat states," the loss of even a small portion of energy can irreversibly distort information, the new states potentially make it easier to recognize such failures and correct them in the future.
Alexey Rubtsov explains that the capabilities of a quantum computer are largely determined by how complex quantum states scientists are able to create and control.
— Many quantum processes can still be modeled on conventional computers. But as quantum states become more complex, computational modes appear that are much more difficult for classical machines to reproduce. Therefore, each new class of states potentially expands the range of tasks available to future quantum computers," says the expert.
However, full-fledged quantum computers are still far away. As Polyakov notes, the current study should be considered rather as an important contribution to the foundation of future technologies.
— This is an important step, but a step into the foundation, not the final assembly. An appropriate comparison: it was not the engine itself that was invented, but a new alloy and a method of processing it, from which the engine can then be made better and more reliable," the expert concludes.
Where quantum technologies are used
Although it may still be years before the advent of mass quantum computers, some quantum technologies are already working today. According to Evgeny Polyakov, Associate professor at the National Research Nuclear University MEPhI, quantum sensors are the first to benefit from the development of this field.
— This direction does not need to wait: atomic clocks, hypersensitive magnetometers and gravimeters are used right now — in navigation, geological exploration, medicine, — the expert notes.
New methods for controlling quantum states, similar to those demonstrated by physicists from Oxford, can make such devices even more accurate. In addition, quantum communication is already developing today, a technology that makes it possible to create data transmission channels that are protected from unnoticed interception.
However, according to Alexey Rubtsov, one of the main directions of their application will be the modeling of complex quantum systems.
— Usually referred to as materials science, quantum chemistry and the development of new substances. We are talking about creating new drugs, batteries, catalysts, fuel cells and other materials, the properties of which can be calculated on a computer even before conducting expensive laboratory experiments," says the scientist.
Today, such tasks require huge computing resources, and in some cases remain inaccessible even to the most powerful supercomputers. Rubtsov also emphasizes that as technology evolves, quantum computing can also find applications in information processing, optimization, and individual search tasks.
Polyakov adds that logistics, supply chain management and the financial sector are considered promising areas, where it is important to quickly analyze a large number of possible scenarios.
How close is the quantum future
Today, Russia has almost all the major technological platforms used in the global quantum race, from ion and atomic systems to photonic and superconducting solutions.
However, as Alexey Rubtsov notes, in terms of a number of key parameters — the number of qubits, the time of their coherence and the accuracy of operations — the country is still inferior to the world leaders.
— According to my estimate, this gap is about three to five years. development is progressing quite quickly, and the gap is not fundamental. It is also important that Russian scientific groups are already able to reproduce complex experimental schemes and work at the level of modern international research," Rubtsov emphasizes.
Looking more broadly, the current stage of development of quantum technologies can be compared with the early era of classical computers, when the first computers occupied entire laboratories and were accessible only to a limited number of specialists. Right now, quantum systems are in about the same position — complex, expensive, and requiring isolation from external influences.
In the coming decades, experts believe, the most likely scenario will be the development of quantum computing through specialized access centers, rather than the emergence of personal devices. Users will solve tasks remotely, and calculations will be performed on powerful quantum installations.
— The main intrigue lies not only in the scaling of the technology, but also in what tasks it will eventually be able to solve faster than classical computers. This is what will define the real boundaries of the quantum revolution," Rubtsov believes.
Thus, quantum technologies have already reached the level of working laboratory systems, but their mass application is a prospect that depends on further scientific and engineering breakthroughs.
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