Quantum calculator: one more problem is solved

To build quantum computers, scientists still face a few challenges. One of the challenges is that quantum computers are vulnerable to the impact of the surrounding environment. External forces can very quickly destroy the information structure of quantum computers, this phenomenon is also called "decoherence" ("decoherence") - as opposed to "coherence".

In order to handle a combination of quantum information, a method related to quantum electrodynamics (QED) is used. In this method, scientists use a small cavity to get the combined kinetics of an atom and a photon - using mirrors to control the radiation properties of an atom. Scientists at the California Institute of Technology (Caltech) are pioneers in this method. Recently, they have announced an important step in creating a distribution of quantum information.

In Physical Review Letters , physicist David Boozer and colleagues of the California Institute of Technology (Caltech, USA) describe the reversible state transition of a combined light pulse comes and comes from the intrinsic state of an atom trapped in the optical cavity. This observation has for the first time verified the hypothesis of atomic physicist Ignacio Cirac about the reversal relationship of quantum states between light and matter using the QED cavity to create a Atomic-photon interaction.

Experimental model (According to Phys. Rev. Lett. 98 (2007) 193601).

"The best result of this study is the illustration of reversibility (ie, coherence) for light emission and absorption processes," Boozer said. "The combination of this process means that it preserves the entire overlap of quantum states, thereby opening the way for connecting quantum information between atoms and light."

Atoms often have a long combined time, acting as " stationary " qubits, or nodes of the network. And photons act like " flying " qubits, they are quantum channels that connect nodes over long distances.

"In principle, in a quantum computer there are several logic gates, each of which performs a basic quantum operation for one or two stationary qubits," Boozer explained. "The logic gates are connected together in a network, so that the output of a port can be moved along a qubit 'to fly' to the input of the next port. find a way to convert stationary qubits into jumping qubits and vice versa, and our study illustrates that. "

With the possibility of reversing the state of the qubit from " flying " to " standing still " and vice versa, scientists have achieved important steps in combining quantum information in a single network. grid, and the outside environment cannot destroy that information.

"In this work, qubits are coded according to the photon number states of light and the super-fine levels of atoms," Boozer said. "In the future, we have a good plan to encode the degrees of freedom of polarization of light and the subunits of atoms in the magnetic field. At the same time we will also study to increase the efficiency of status transmission " . ( See details of the work in Phys. Rev. Lett. 98, 193601 (2007) ).

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