A photon with a trillion atoms crossed

Physicists can cache information in a large group of restricted rubidium atoms.

A single photon is entangled with a whole group of atoms. © University of Warsaw / M. Dabrowski
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Nuclear lumps in the quantum state: For the first time, researchers have entangled a photon with a macroscopic object - a lump of one billion atoms. They were able to transfer information from a photon to the entire group of rubidium atoms and retrieve it. In addition, the entanglement remained stable for several microseconds - also an important step forward.

The future of information technology lies in quantum computers. These should process large amounts of data within a very short time. This is possible thanks to simultaneous arithmetic operations based on the superposition of states - also known as quantum entanglement. When two particles are entangled with each other, information about their condition can be read out on both the one particle and the other particle.

While often the short lifespan of such quantum entangled states is a hurdle, physicists have now achieved a proverbial quantum leap, especially in the size of the entangled system.

Entanglement in a big way

The team headed by Wojciech Wasilewski at the Quantum Memories Laboratory in Warsaw has managed to interlock a single photon with one trillion hot Rubidium atoms. They irradiated the atoms with a laser and recorded individual photons of the scattered light with special cameras.

Analyzes revealed that the photon was entangled with the entire atomic group with respect to its momentum. "A single detected photon carries information about the quantum state of the entire atomic group, " explains Michal Dabrowski of the University of Warsaw. This is the first time that the entanglement of a photon with such a large object has succeeded. display

Well suited as a quantum memory

Michal Dabrowski points out the great advantage: "These atoms can be stored and their quantum state read at any time." "The atoms store the photon in the form of a wave of atomic spins, which extends in our structure over a trillion atoms, " Michal leads Parniak continues. "Such a state also copes with the loss of individual atoms, because the information is distributed over a large number of particles."

The researchers also managed to stabilize the constrained state for a relatively long time: "We were able to maintain the multi-dimensional constraint for a few microseconds, which is about one thousand times longer than in previous experiments and at the same time long enough to carry out quantum calculations for the atomic state, "says Wojciech Wasilewski.

Such photon-atom constraints could therefore be suitable as building blocks for future quantum computers. In their experiment, the Warsaw physicists were able to simultaneously store the quantum information of twelve photons in such atomic quantum stores. This capacity is promising with regard to the development of powerful quantum computers. (Optica, 2017; doi: 10.1364 / OPTICA.4.000272)

(University of Warsaw, 03.03.2017 - CLU)