A method of securely communicating between multiple quantum devices has been developed by a UCL-led team of scientists, bringing forward the reality of a large-scale, un- hackable quantum network.
To date, communicating via quantum networks has only been possible between two devices of known provenance that have been built securely.
With the EU and UK committing €1 billion and £270 million respectively into funding quantum technology research, a race is on to develop the first truly secure, large-scale network between cities that works for any quantum device.
From afar, it looks like a steampunk chandelier. An intricate collection of tubes and wires that culminate in a small steel cylinder at the bottom. It is, in fact, one of the most sophisticated quantum computers ever built. The processor inside has 50 quantum bits, or qubits, that process tasks in a (potentially) revolutionary way. Normally, information is created and stored as a series of ones and zeroes. Qubits can represent both values at the same time (known as superposition), which means a quantum computer can theoretically test the two simultaneously. Add more qubits and this hard-to-believe computational power increases.
Last November, IBM unveiled the world’s first 50-qubit quantum computer. It lives in a laboratory, inside a giant white case, with pumps to keep it cool and some traditional computers to manage the tasks or algorithms being initiated. At CES this year, the company brought the innards — the wires and tubes required to send signals to the chip and keep the system cool — so reporters and attendees could better understand how it works. The biggest challenge, IBM Research Vice President Jeffrey Welser told me, is isolating the chip from unwanted “noise.” This includes electrical, magnetic and thermal noise — just the temperature of the room renders the whole machine useless.
Researchers at Princeton University have constructed silicon hardware that can control quantum behaviour between two electrons with extremely high precision.
The team constructed a two qubit gate that controls interactions between the electrons in a way that allows them to act as the qubits necessary for quantum computing. The demonstration of the gate is being seen as an early step in building a more complex quantum computing device from silicon.
The gate was constructed by layering aluminium wires onto a highly ordered silicon crystal. The wires deliver voltages that trap two single electrons, separated by an energy barrier, in a double quantum dot.
A new conception of quantum mechanics rests on the idea that parallel universes exist, and that they interact with our own to create weird and wonderful quantum phenomena.
A team from Griffith’s Centre for Quantum Dynamics in Australia have demonstrated how to rigorously test if pairs of photons — particles of light — display Einstein’s “spooky action at a distance”, even under adverse conditions that mimic those outside the lab.
They demonstrated that the effect, also known as quantum nonlocality, can still be verified even when many of the photons are lost by absorption or scattering as they travel from source to destination through an optical fiber channel. The experimental study and techniques are published in the journal Science Advances.
Quantum nonlocality is important in the development of new global quantum information networks, which will have transmission security guaranteed by the laws of physics. These are the networks where powerful quantum computers can be linked.
We’re used to dealing with three physical dimensions and one extra dimension of time as we move through the Universe, but two teams of scientists have shown that a fourth spatial dimension could reach beyond the limits of up and down, left and right, and forwards and backwards.
As you might expect given this is bending the laws of physics, the experiments involved are partly theoretical and very complex, and touch on our old friend quantum mechanics.
By placing together two specially designed 2D setups, two separate teams of researchers — one in Europe and one in the US — were able to catch a glimpse of this fourth spatial dimension through what’s known as the quantum Hall effect, a certain way of restricting and measuring electrons.
To the best of our knowledge, we humans can only experience this world in three spatial dimensions (plus one time dimension): up and down, left and right, and forward and backward. But in two physics labs, scientists have found a way to represent a fourth spatial dimension.
This isn’t a fourth dimension that you can disappear into or anything like that. Instead, two teams of physicists engineered special two-dimensional setups, one with ultra-cold atoms and another with light particles. Both cases demonstrated different but complementary outcomes that looked the same as something called the “quantum Hall effect” occurring in four dimensions. These experiments could have important implications to fundamental science, or even allow engineers to access higher-dimension physics in our lower-dimension world.
“Physically, we don’t have a 4D spatial system, but we can access 4D quantum Hall physics using this lower-dimensional system because the higher-dimensional system is coded in the complexity of the structure,” Mikael Rechtsman, professor at Penn State University behind one of the papers, told Gizmodo. “Maybe we can come up with new physics in the higher dimension and then design devices that take advantage the higher-dimensional physics in lower dimensions.”
For the first time, physicists have built a two-dimensional experimental system that allows them to study the physical properties of materials that were theorized to exist only in four-dimensional space. An international team of researchers from Penn State, ETH Zurich in Switzerland, the University of Pittsburgh, and the Holon Institute of Technology in Israel have demonstrated that the behavior of particles of light can be made to match predictions about the four-dimensional version of the “quantum Hall effect”—a phenomenon that has been at the root of three Nobel Prizes in physics—in a two-dimensional array of “waveguides.”
A paper describing the research appears January 4, 2018 in the journal Nature along with a paper from a separate group from Germany that shows that a similar mechanism can be used to make a gas of ultracold atoms exhibit four-dimensional quantum Hall physics as well.
“When it was theorized that the quantum Hall effect could be observed in four-dimensional space,” said Mikael Rechtsman, assistant professor of physics and an author of the paper, “it was considered to be of purely theoretical interest because the real world consists of only three spatial dimensions; it was more or less a curiosity. But, we have now shown that four-dimensional quantum Hall physics can be emulated using photons—particles of light—flowing through an intricately structured piece of glass—a waveguide array.”
