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Catalyst recipes for transforming quantum states

Catalytic conversion by local operation and classical communication.Credit: Center for Quantum Optical Technology, University of Warsaw

Quantum physicists at the University of Warsaw have discovered new applications for quantum catalysts. This is a quantum equivalent to the chemical catalysts used in industry, revealing that quantum catalysts are useful in far more setups than previously known. Breakthroughs can prove to be crucial in future quantum key distribution networks or distributed quantum computing.


Team Quantum physicist The Center for Quantum Optical Technology at the University of Warsaw, Poland, has found a complete solution to the daunting question of whether catalytic conversion from one early quantum state to another desirable quantum state is possible.Results of their study — published on October 5, 2021 Physical review letter-Prove the usefulness of catalysts in facilitating quantum processes, Entanglement Available for: Quantum information processing.. Breakthroughs are especially relevant for quantum technologies that involve two or more distant laboratories. For example, quantum key distribution networks and distributed quantum computing.

Entanglement is an important function of quantum mechanics, and in fact most quantum technologies have been developed. In its simplest form, it occurs as a correlation between two distant parties, such as Alice and Bob.The degree of entanglement of a given quantum system is given by the entanglement. entropy, This provides information on how efficient quantum communication between Alice and Bob is.

Prior to this work, entanglement entropy only occurs when the two parties exchange many signals, as Alexander Streltsov, co-author of the paper with Tulja Varun Kondra and Chandan Datta, explains: It made sense. If you know that the coin is fair, you know nothing about the result of the flip. Entropy only makes asymptotic meaning, “he says. “Similar to entanglement entropy, entropy doesn’t make much sense if Alice and Bob share only one instance of the quantum state.”

To overcome this, the international team introduced a theoretically intertwined catalyst into the mixture.

The entangled catalyst is a quantum system that is not modified by the process under consideration, similar to the catalysts used in the industry to speed up chemical reactions without being consumed in the process, but it affects the process. Allows conversions that would not be possible without it. Specific examples of intertwined catalysts that induce transformations were proposed as early as 1999, but it was not previously known which other quantum states could be achieved by adding catalysts.

Streltsov and co-workers have theoretically proved that entanglement entropy has physical significance in the presence of a suitable catalyst, even when only a single instance of pure quantum state is available. In fact, entanglement entropy fully characterizes the transformation in this situation. From this, researchers have shown how to predict which transformations are actually possible. “We have found a complete solution to the question of whether catalytic transfer is possible,” Streltsov confirms.

This new knowledge has many practical future applications. For example, in quantum cryptography, if Alice and Bob want to establish secure communication, they can share what is called a singlet. The singlet is the optimal quantum state of two quantum bits (qubits). If Alice holds one of the qubits and Bob holds the other, you can extract a completely secure key by running a specific protocol. The work of Streltsov and his colleagues provides a way to know which quantum states can be converted to singlets and then used by Alice and Bob.

Streltsov et al. Apply techniques to more complex quantum information tasks than transforming one quantum state into another, and are a method of optimally transmitting information using entanglement and classical communication. Clarified how the catalyst can enhance the efficiency of merging. Among other applications, the results can be applied to show how entangled catalysts make noisy conditions useful in quantum cryptography. “If there is a lot of noise in the state, the standard quantum cryptography protocol will not give good results in the end,” says Streltsov.But if the process is enhanced by adding entanglements catalyst For example, qubits can be swapped at both ends of a noisy fiber optic without compromising the process. “Even if the fiber is very noisy, this can, in principle, achieve very good efficiency,” Streltsov adds.


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For more information:
Tulja Varun Kondra et al, Catalytic conversion of pure entangled state, Physical review letter (2021). DOI: 10.1103 / PhysRevLett.127.150503

Quote: The catalyst recipe for converting quantum states (November 29, 2021) can be found at https://phys.org/news/2021-11-catalytic-recipe-quantum-states.html on November 29, 2021. Was acquired in.

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