The quantum internet just got one step closer to reality thanks to new resonator breakthrough

A new kind of resonator has the ability to transmit quantum information using single photons from a silicon device tipped with a few dozen erbium atoms.
John Loeffler
A nanophotonic resonator
A nanophotonic resonator

Max Planck Institute of Quantum Optics 

The quantum internet just got one step closer to reality thanks to a new breakthrough that allows the encoded quantum information to be transmitted over distance.

The quantum internet offers the promise of perfect information security on a quantum mechanical level in the transmission of information using qubits, which will decompose into random information if anyone were to try and intercept it.

"All quantum technologies are based on so-called qubits, the elementary carriers of quantum information," Prof. Dr. Andreas Reiserer, of the Max Planck Institute of Quantum Optics and the Technical University of Munich, said in a statement. Connecting quantum systems together, then, requires the transmission of these qubits between quantum systems.

The researchers have found a way to do exactly that, using erbium atoms implanted into silicon which, when excited by light using a fiberoptic cable, will emit single photons encoded with this quantum information.

"However, in order to make technical use of these fundamental properties of erbium, one has to stimulate the atoms to emit individual light particles in a controlled manner," Andreas Gritsch, a doctoral researcher in Reiserer's team at the MPQ, said. "In this way, an interface for sending or receiving quantum information can be created."

Specifically, the nanophotonic resonator that the erbium atoms create has ideal properties for communicating information, since they emit light at the wavelength of 1,536 nanometers, which is identical to the wavelength used in classical communications over a fiberoptic network.

Unlike classical networks though, this resonator does not require mirrors like other optical resonators, instead using a special crystalline silicon with regular holes in the material only nanometers across. In all, the entire resonator is only a few micrometers in size and contains only dozens of erbium atoms in total.

"The fact that this is possible in crystalline silicon offers an additional opportunity for the realization of quantum networks," Reiserer said, "because this material has been used for decades to produce classic semiconductor elements, for example microchips for computers, smartphones or navigation devices."

Ideally, this would mean that the manufacturing infrastructure is already in place to create these new resonators once more quantum systems are ready to be networked together.

"This means that for quantum technology applications, such as the construction of quantum networks, silicon crystals can also be produced in high quality and purity," Reiserer added.

The new research was published this week in the journal Optica.

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