Abstract-Quantum computing Hyper Terahertz Facility

Kulvinder Singh Chadha

http://iopscience.iop.org/article/10.1088/2058-7058/29/1/17

A new facility has opened at the University of Surrey to use terahertz radiation for quantum computing. The Hyper Terahertz Facility (HTF) is a joint collaboration between the University of Surrey and the National Physical Laboratory (NPL).

Cartoon coyote's fall inspires development of new properties of silicon

Scientists have discovered a new type of silicon that could be used to control light beams in a new kind of photonic chip -- a chipset where information is carried by light beams rather than electrical currents.

University of Surrey
https://www.sciencedaily.com/releases/2018/02/180227115601.htm

The essence of the technology -- where an object takes a moment to respond to the energy placed upon it -- is a staple of cartoons such as Roadrunner, where characters run off cliffs and spend a moment in mid-air before falling.

Scientists hope that their discovery, detailed in a study published by Nature Photonics, will lead to the development of more exciting technologies such as signal modulators for terahertz (THz) beams -- which is part of the electromagnetic spectrum between visible/infrared light and radio/microwaves.

Silicon is widely used to send microwave signals for mobile communications, but it is very poor at sending visible light signals. The team discovered that the standard impurities that are sprinkled into ordinary computer chips to make transistors can control the flow of THz photons far more efficiently than almost anything else. This has the double benefit of potentially allowing a new method of chip-to-chip communication with silicon, currently only possible with much more expensive materials, but also pushing mobile communications to much higher frequency and allowing the transmission of more data.

The signal modulation effect works by using two or more photons, each of which could individually go straight through the silicon unhindered, and only when they arrive together they get absorbed. The first photon acts like a switch -- its presence or absence determines what will happen to the others. The catch is that the second photon has to be almost simultaneous with the first, meaning that the intensity of the beams must be really high. The researchers tried using THz photons instead of the infrared photons used in all previous attempts, and found that they could get switching with thousands of times lower intensity than ever before.

Professor Ben Murdin from the University of Surrey, said: "It's just like when Wile E. Coyote is chasing the Roadrunner and goes off the edge of a cliff -- there's always a moment before physics wakes up and realises he has too much potential energy and he falls. During this 'coyote time' (as gamers call it) sometimes something else can take effect like a rocket or a stone or a jump. That's exactly how Heisenberg's Uncertainty Principle works here -- there's a little bit of 'coyote time' after the first photon hits in which the molecule doesn't know what energy it's supposed to have, but the more energy it tries to ignore the less the coyote time available.

"We found that with terahertz light silicon's coyote time is much, much longer, meaning this kind of photon switch is far more efficient than anything else we know of. The results show that silicon may have a completely new lease of life, providing new ways to control information with light rather than electrical current, meaning far faster computers and higher bandwidth communications."

Dr. Daniel Mittleman gives Terahertztechnology readers a glimpse of activites at TeraNano meeting in Japan

Hi Randy,

I’m writing from the TeraNano meeting, to give you a summary of just a few of the highlights. This conference is an annual review associated with the PIRE (Partnerships for International Research and Education) program at RiceUniversity which is sponsored by the National Science Foundation (among others). This program is run by Professor Junichiro Kono (my colleague at Rice) and Professor Masa Tonouchi from Osaka University. It funds student exchange between the US and Japan, and has been a very successful vehicle for a lot of fruitful research collaborations. It focuses on the science at the overlap between terahertz spectroscopy and nano-materials, hence the name ‘TeraNano’.

Consistent with the mission of NSF-funded activities, the subject matter here this week is very much basic research. A lot of the research being discussed here involves the use of terahertz to study carbon nanostructures, especially graphene (a single layer of carbon atoms in a hexagonal lattice). This is clearly the ‘material of the moment’, since there is a lot of optimism associated with potential applications in electronics, transparent displays, opto-electronics, and so on. It turns out that a lot of the interesting possible applications of graphene can be studied using terahertz techniques, so there is a natural overlap between the two fields. One nice highlight here was the talk by Berardi Sensale-Rodriguez (University of Notre Dame) on the use of graphene as a modulator for terahertz radiation. This device could eventually be used to switch terahertz beams on and off electrically at high speed, a capability which is currently not easy to do by other means. Beyond graphene, I would also mention an interesting talk by Ben Murdin (University of Surrey), who is investigating the use of single-atom impurities in silicon for quantum computing – can we use one phosphorus atom to store one bit of information in its quantum state? If so, then controlling those individual bits could be accomplished using terahertz radiation. My own talk was inspired by my group’s recent work on using parallel metal plates for guiding terahertz waves. We’ve been thinking about how to engineer the amount of radiation that emerges from the wave guide at the output end, and we now have some nice results on minimizing this output, making a (nearly) perfect reflector. This could lead to a waveguide-based resonator, where the radiation is trapped inside the waveguide by these nearly perfect reflections at all output facets.

This afternoon, we have also heard several talks on the integration of terahertz science and technology into educational missions at various levels. Of course, the TeraNano program has ongoing self-evaluation of its effectiveness at the undergraduate and graduate level. But there is also now an effort to bring simple terahertz experiments into high schools, which can help to inspire students to pursue STEM fields when they get to college.

I would also like to put in a small advertisement for a fledgling activity at Rice University. Several of my colleagues and I are organizing an effort to initiate a new seminar series at Rice in the topical areas of terahertz, infrared, and millimeter-wave science and technology. We hope to launch this seminar series early next year, to have regularly scheduled speakers at Rice in these fields. I would welcome suggestions of possible speakers from the readers of your blog, and of course anybody who is in the Houston area would be welcome to attend any of the talks.

Regards,

Dan Mittleman