A novel material that consists of a single sheet of carbon atoms could lead to new designs for optical quantum computers. Physicists from the University of Vienna and the Institute of Photonic Sciences in Barcelona have shown that tailored graphene structures enable single photons to interact with each other. The proposed new architecture for quantum computer is published in the recent issue of npj Quantum Information.
Photons barely interact with the environment, making them a leading candidate for storing and transmitting quantum information. This same feature makes it especially difficult to manipulate information that is encoded in photons.
In order to build a photonic quantum computer, one photon must change the state of a second. Such a device is called a quantum logic gate, and millions of logic gates will be needed to build a quantum computer.
One way to achieve this is to use a so-called 'nonlinear material' wherein two photons interact within the material. Unfortunately, standard nonlinear materials are far too inefficient to build a quantum logic gate.
It was recently realized that nonlinear interactions can be greatly enhanced by using plasmons. In a plasmon, light is bound to electrons on the surface of the material. These electrons can then help the photons to interact much more strongly. However, plasmons in standard materials decay before the needed quantum effects can take place.
In their new work, the team of scientists led by Prof. Philip Walther at the University of Vienna propose to create plasmons in graphene. This 2D material discovered barely a decade ago consists of a single layer of carbon atoms arranged in a honeycomb structure, and, since its discovery, it has not stopped surprising us.
For this particular purpose, the peculiar configuration of the electrons in graphene leads to both an extremely strong nonlinear interaction and plasmons that live for an exceptionally long time.
In their proposed graphene quantum logic gate, the scientists show that if single plasmons are created in nanoribbons made out of graphene, two plasmons in different nanoribbons can interact through their electric fields. Provided that each plasmon stays in its ribbon multiple gates can be applied to the plasmons which is required for quantum computation.
"We have shown that the strong nonlinear interaction in graphene makes it impossible for two plasmons to hop into the same ribbon" confirms Irati Alonso Calafell, first-author of this work.
Their proposed scheme makes use of several unique properties of graphene, each of which has been observed individually. The team in Vienna is currently performing experimental measurements on a similar graphene-based system to confirm the feasibility of their gate with current technology. Since the gate is naturally small, and operates at room temperature it should readily lend itself to being scaled up, as is required for many quantum technologies.
Quantum computing with graphene plasmons, I. Alonso Calafell, J. D. Cox, M. Radonji, J. R. M. Saavedra, F. J. García de Abajo, L. A. Rozema & P. Walther. npj Quantum Information 5, 37 (2019). DOI: 10.1038/s41534-019-0150-2
Philip Walther | EurekAlert!
No more traffic blues for information transfer: decongesting wireless channels
11.11.2019 | Tokyo University of Science
A new quantum data classification protocol brings us nearer to a future 'quantum internet'
11.11.2019 | Universitat Autonoma de Barcelona
If you've ever tried to put several really strong, small cube magnets right next to each other on a magnetic board, you'll know that you just can't do it. What happens is that the magnets always arrange themselves in a column sticking out vertically from the magnetic board. Moreover, it's almost impossible to join several rows of these magnets together to form a flat surface. That's because magnets are dipolar. Equal poles repel each other, with the north pole of one magnet always attaching itself to the south pole of another and vice versa. This explains why they form a column with all the magnets aligned the same way.
Now, scientists at ETH Zurich have managed to create magnetic building blocks in the shape of cubes that - for the first time ever - can be joined together to...
Quantum-based communication and computation technologies promise unprecedented applications, such as unconditionally secure communications, ultra-precise...
In two experiments performed at the free-electron laser FLASH in Hamburg a cooperation led by physicists from the Heidelberg Max Planck Institute for Nuclear physics (MPIK) demonstrated strongly-driven nonlinear interaction of ultrashort extreme-ultraviolet (XUV) laser pulses with atoms and ions. The powerful excitation of an electron pair in helium was found to compete with the ultrafast decay, which temporarily may even lead to population inversion. Resonant transitions in doubly charged neon ions were shifted in energy, and observed by XUV-XUV pump-probe transient absorption spectroscopy.
An international team led by physicists from the MPIK reports on new results for efficient two-electron excitations in helium driven by strong and ultrashort...
An international research group has observed new quantum properties on an artificial giant atom and has now published its results in the high-ranking journal Nature Physics. The quantum system under investigation apparently has a memory - a new finding that could be used to build a quantum computer.
The research group, consisting of German, Swedish and Indian scientists, has investigated an artificial quantum system and found new properties.
Researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory have reported a new mechanism to speed up the charging of lithium-ion...
05.11.2019 | Event News
30.10.2019 | Event News
02.10.2019 | Event News
12.11.2019 | Machine Engineering
12.11.2019 | Power and Electrical Engineering
12.11.2019 | Physics and Astronomy