Prof Ben Murdin has published an article on theconversation.com explaining why better clocks are needed and how. See full details here.
In April 2018, Dr. Nicole Li undertook a self-funded speaking tour in China aiming to inspire future generations with her own story and cutting edge sciences. She travelled over 20,000 miles, visited 7 cities, including China’s first and second tier cities including Beijing, Shanghai, Shenzhen and Chengdu as well as more rural areas which include places like Taiyuan, Nanchong and Urumqi, gave 11 talks over a period of 16 days, and presented to 2000+ people including school children and parents. All the talks where free for the public to participate.
Nicole grew up in rural China; by dreaming big and working hard she has managed to achieve the seemingly impossible. In her talks, she told the audience her story including being a female scientist and hoping to encourage more girls to choose STEM subjects. She also shared her passion in science with the audience by explaining her research project ADDRFSS as well as 5G, FAIR-SPACE and other scientific research activities that have been conducted at Surrey University.
Nicole was also invited to be interviewed by a popular mainstream radio programme for an hour in Urumqi, and took several live calls from children, including a girl, who wish to become scientists.
Orgaising and performing in such events in a short time scale requires lots of hard work. Nicole was pleased to see such positive feedback from the audience. Some later contacted her saying they had never had a chance to attend such an event before, and to be influenced in such positive ways. Nicole said “Some of my friends worried that the whole agenda would be too much for me, and suggested I stay with the top level cities. But I said children in cities like Beijing and Shanghai have many resources and felt the children in the rural areas needed the help the most.”
The SIMPLE tool, a new single atom implanter, has arrived at Surrey this week. The tool should allow the injection of single atoms of a range of species into practically any substrate with a target accuracy about ten nanometers. The tool is unique as it will be capable of counting the atoms one-by-one as they arrive, whereas traditional implanters can only implant single atoms by trial and error – the means that you only get the desired single atom a third of the time, and a third of the time you get none and another third of the time you get more than one. The SIMPLE tool (which stands for Single Ion Multispecies Positioning at Low Energy) will start by implanting bismuth atoms into silicon crystals for quantum information “qubits”, where information is held in superposition states so the bismuth atom is spinning both clock-wise and anti-clockwise simultaneously, in a collaboration with the silicon quantum technology group at Surrey (known as the ADDRFSS team). The tool has been developed by Ionoptika and Surrey, with Surrey doctoral student Nathan Cassidy who spent the first couple of years of his study at the company.
Prof Ben Murdin gave a talk entitled “Two photon absorption: a tribute to the second most important female physicist of all time, on International Women’s Day” at University of Surrey on 8th March 2018.
Two-photon absorption is a quantum physics effect with no classical analogue, that makes it possible to jump twice as high as you might otherwise think. It is important for measurement of CPT symmetry violation of antimatter using anti-hydrogen, and is responsible for the way green laser pointers work. In this seminar I will talk about the invention of the effect, and the recent discovery by our group, published in this month’s issue of Nature Photonics, that the environment that provides the best two-photon absorption is a plain old silicon crystal.
An international team of scientists, led by the University of Surrey, has 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.
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.”
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The TEDx talk, which took place in Shanghai’s Fuxing Park Expo exhibition hall on 22 April, was themed on ‘Back to the Future’. The famous film trilogy, where the main character travels back in time to put things right for the future, raises important questions about whether the future is determined by destiny or free will – a topic that was tackled at the TEDx talk by a diverse range of international speakers from industry and academia.
During his talk, Professor Murdin highlighted the advances the University is making in the field of quantum technology, which is based on manipulating individual electrons to behave and interact in a certain way.
Speaking before the talk, Ben explained: “My talk will focus on how old technology is getting a new life. Silicon chips have been used for electronic devices since the late ‘50s, and the challenge was to get crystals of higher and higher purity, but then to create deliberate defects and impurities to control the flow of electrical signals through the chip.
“Today, in our quest for quantum technology, we need to understand and control the quantum motion of electrons as they orbit the defects. The simplest, but also one of the weirdest of these quantum effects we can now produce is ‘time reversal’, where time runs backwards for the electrons – and you trigger it with a flash of light, just like Marty McFly in the ‘Back to the Future’ movie.”
The TEDx talk was a great success, with an audience of over 400 gathered to delve into the world of quantum technology and satisfy their curiosity about time travel. The event was also live-streamed.
Ben commented: “It was great to be able to visit Shanghai and some scientist colleagues to see how we can collaborate, because China is so dynamic and fast-moving. It was terrific to see so many people interested in coming to a science talk by a physicist. I hope I captured the imagination by showing how useful “time travel” is, even if it’s only possible for very tiny objects and for very short times.
“Giving the talk and meeting people at the TEDx conference gave me inspiration for how to teach the physics better to the students back home at the University of Surrey, so I’m looking forward to next semester!”
The global TEDx programme is designed to help communities, organisations and individuals to spark conversation and connection through local ‘TED-like’ experiences. TED (Technology, Entertainment, Design) is a non-profit organisation which posts talks online under the slogan ‘ideas worth spreading’.
For more information on Professor Murdin’s TEDx Talk, please contact Dr Juerong (Nicole) Li at email@example.com.
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Newly published research from the collaboration shows that we can control the shape and size of phosphorous atoms in the silicon crystal (Si:P). Our international team studied the structure of Si:P orbitals under magnetic fields, where simple theoretical models tell us that the electron should wiggle and rotate around the nucleus. We created superpositions between three states using the free-electron laser FELIX, and studied how the Si:P absorbed different amounts of light at different times. This told us something about how the atoms’ behaviour related to the simple theoretical models.
We then noticed that the simple theoretical models didn’t explain very well why they should apply to complicated systems such as Si:P. So we worked out a theoretical explanation for our data which captured lots more of the detail, which is specific to silicon and makes everything more complicated. We showed that, despite the complicated formulation, it could be quite easily compacted into a set of equations which behave much like the simpler theoretical models which we started with. That means that we have a simple concept for why the atoms dance about, and a very strong link to the real underlying physics.
Our most interesting result was when we plotted the shape of the wavefunctions, and how they evolve over time. We found that when they rotate around, there are places near the atom where the probability of finding the electron goes up and down over time. That means that if we put other atoms nearby, we can control which nearby atoms our qubit “sees” at any given time. We came up with a new suggestion for how to take advantage of this so that future quantum computers made with silicon could be more robust to random errors – a very important milestone in the development of and quantum computer!
Finally, we remembered the old adage of Richard Feynman that if you can’t explain a concept to an undergraduate then you don’t understand it well enough. So we took on board a project student, Charlie, to test this out – and from our explanations he produced a series of animations showing how the wavefunctions dance around in 3D space.