Oct
19
2:30 PM14:30

Quantum Colloquium: Electrical contacts between three-dimensional metals and two-dimensional semiconductors

  • Cavendish Laboratory Small Lecture Theatre (map)
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Manish Chhowalla (University of Cambridge, UK)

As the dimensions of semiconducting channels in field effect transistors (FETs) decrease, the contact resistance of metal-semiconductor interface at the source and drain electrodes dominates the performance. Two dimensional (2D) transitional metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) have been demonstrated to be excellent semi-conductors for ultra-thin FETs. However, unusually high contact resistance has been observed across the metal-2D TMD interface. We have shown that it is possible to reduce the contact resistance by forming lateral junctions between metallic and semiconducting phases of 2D materials. Recent studies have shown that van der Waals (vdW) contacts formed by graphene on 2D TMDs provide lowest contact resistance. However, vdW contacts between evaporated three-dimensional metal and 2D TMDs have yet to be demonstrated. Here, we report the realization of ultra-clean vdW contacts between 3D metals and single layer MoS2. Using scanning transmission electron microscopy (STEM) imaging, we show that the 3D metal and 2D MoS2 interface is atomically sharp with no detectable chemical interaction, suggesting van-der-Waals-type bonding between the metal and MoS2. We show that the contact resistance of indium electrodes is ~ 800 Ω-μm - amongst the lowest observed for metal electrodes on MoS2 and is translated into high performance FETs with mobility in excess of 160 cm2-V-s-1 at room temperature without encapsulation. We also demonstrate low contact resistance of 220 Ω-μm on 2D NbS2 and near ideal band offsets, indicative of defect free interfaces, in WS2 and WSe2. I will introduce 2D TMDs and their properties and then describe our efforts on making good contacts on 2D semiconductors.

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Oct
4
2:00 PM14:00

Quantum Colloquium: Spotting the elusive Majorana under the microscope

Ali Yazdani (Princeton University, USA)

Ettore Majorana famously considered that there may be fermions in nature that are their own antiparticle — and then he mysteriously disappeared just after proposing the idea in 1938. In recent years, following pioneering theoretical work of Kitaev and others, we have learned how to engineer materials that harbor quasiparticles that behave similar to fermions Majorana had envisioned. In particular, there has been a focus on one-dimensional topological superconductor that harbor Majorana zero modes (MZM) that can potentially be used to make fault-tolerant topological quantum computation possible. Recently, we have proposed and implemented a platform for realization of topological superconductivity and MZM in chains of magnetic atoms on the surface of a superconductor [1,2]. In this talk, I will describe this platform and the series of experiments we have performed to establish the presence of these exotic quasi-particle using spectroscopic mapping with the scanning tunneling microscope (STM). [2-4] These include study of the unique spin signature of MZM.[4] Finally, if there is time I will discuss our most recent work on realization of MZM in a platform based on chiral quantum spin Hall edge states. Overall these experiments, illustrate how the power of spectroscopic imaging with the STM can be used to visualize novel quantum states of matter and their exotic quasi-particles.

[1] S. Nadj-Perge et al. PRB 88, 020407 (2013).
[2] S. Nadj-Perge et al. Science 346, 6209 (2014).
[3] B. E. Feldman et al. Nature Physics 13, 286 (2016).
[4] S. Jeon et al. Science 358, 772 (2017).

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Nov
29
11:30 AM11:30

Quantum Seminar: Scalable quantum information processing in diamond

William J Munro (NTT Corporation, Japan)

Physics and information are intimately connected, and the ultimate information processing devices will be those that harness the principles of quantum mechanics. Many physical systems have been identified as candidates for quantum information processing, but none of them are immune from errors. The challenge remains to find a path from the experiments of today to a reliable and scalable quantum information processing devices. Here, we develop an architecture based on a simple module comprising an optical cavity containing a single negatively charged nitrogen vacancy center in diamond. Modules are connected by photons propagating in a fiber-optical network. We find that our architecture enables large-scale quantum information processing with existing technology.

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Oct
19
5:00 PM17:00

Quantum Cambridge Colloquium

Speaker: Prof Charles Bennett (IBM)

Time: 5pm on Monday 19th October

Location: Central Core of the Centre for Mathematical Sciences, Clarkson Road

 

Computation, Dynamics, Evidence, and Experience

Like other parts of mathematics, information and computation theory originated as abstractions of experience, but their 20th century founders left behind, as mere physics, important thermodynamic and quantum ideas whose subsequent incorporation has greatly enriched the mathematical theory.  Aside from its internal elegance, the new theory provides a deeper understanding of natural phenomena, such how thermodynamic disequilibrium enables the emergence of classical phenomenology from quantum laws, and the subsequent emergence of "logically deep" structures, containing internal evidence of a nontrivial history.

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Sep
10
1:00 PM13:00

EPSRC Quantum Technologies Pump-Priming Collaboration Workshop

EPSRC Quantum Technologies Pump-Priming Collaboration Workshop is taking place on September 10, 2015 at the Cavendish Laboratory.

All funded researchers will be presenting their latest results and the schedule is as follows:

 

Agenda

1:30 pm  Welcome and introduction to the workshop – Mete Atature

A recap of the Quantum Cambridge Winter School 2015 – Aga Iwasiewicz-Wabnig

1:45 pm  Session 1 – short talks and discussion:  Chaired by Celestino Creatore

Modelling quantum coherent electron systems” David Arvidsson Shukur

InGaN quantum dots in GaN nanowires for polarisation controlled, wavelength multiplexed and electrically driven single-photon emitters” Lucy Goff

Magnetic insulators for quantum inter-conversion” Stefan Lagenfeld

Building collaborations: Exploring spin polarisation in graphene” David Love

Topological Insulators: Synthesis of novel materials for quantum-enhanced devices” Angadjit Singh

Building collaborations in quantum cryptography” Adrian Kent

2:45 pm  Coffee break

3:00 pmSession 2 – short talks and discussion: Chaired by David Love

Two Dimensional Crystals for Quantum Science and Technology” Carmen Palacios-Berraquero and Matteo Barbone

Long distance transport of qubits in silicon using surface acoustic waves” Tzu-Kan Hsiao

A high-speed millikelvin nanopositioner for quantum readout of superconducting devices” Malcolm Connolly

Exploring, controlling and exploiting quantum effects in biologically inspired DNA nanostructures Celestino Creatore

Single photon characteristics in hybrid quantum-classical photonic systems” Adrian Wonfor

4:00 pm  Closing remarks and further networking

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Apr
21
6:45 PM18:45

A Debate on Quantum Computing

http://www.jbs.cam.ac.uk/media/events/towngown-quantumcomputing/

21 April 2015 18:45-20:30

“Debate: This house believes that quantum computing, while scientifically interesting, will not make a practical difference to society in our lifetime”

Proposition: Dr Hermann Hauser, Co-Founder of Amadeus Capital Partners
Opposition: Ilyas Khan, Leader in Residence and Fellow in Management Practice, Cambridge Judge Business School and Aram Harrow, Assistant Professor of Physics, Massachusetts Institute of Technology

Town & Gown: Where Business & Academia Collide, a new series hosted by Cambridge Judge Business School, will bring the business and academic worlds together through thought-provoking debate. From technology to philosophy, topics will be addressed from academic and business viewpoints and you can expect to be challenged and stimulated by what you hear. Networking and drinks follow the debate where we encourage you to carry on the conversation.

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Mar
20
to Mar 23

Winter School 2015

A fully-funded winter school for PhD students and postdocs of Cambridge!

This event offers a great opportunity to find out about research conducted by other research groups, create new links and learn from exciting lectures delivered by internationally renowned speakers from both UK and overseas. The lectures will be on a wide range of research fields including superconducting qubits, quantum optomechanics, ultracold atoms, topological light and quantum thermodynamics to list a few. The school will also include talks and posters by the participants, as well as discussion and interactive sessions. There will also be an opportunity to visit the Quantum Hub ‘NQIT’ based at the University of Oxford – one of the four brand new UK Quantum Technologies Hubs, where University of Cambridge is a partner institution.

The school is fully funded for all participants and is aimed to increase interconnectivity within the Quantum Cambridge community, taking a bottom-up approach with primary focus on the early career researchers.

Click here for the Announcement Poster!

Confirmed lecturers include Janet Anders, Chris Bell, Alex Chin, Andrew Ferguson, Ivette Fuentes, Zoran Hadzibabic, Marko Loncar, Gavin Morley, Andreas Nunnenkamp, Akshay Rao, Uli Schneider, Suchitra Sebastian, John Teufel, Jake Taylor, Hakan Tureci and Andreas Wallraff.

If you have any questions about the workshop, please email Aga (ai261@cam.ac.uk).

 

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Mar
18
to Mar 19

NEW FRONTIERS FOR QUANTUM TECHNOLOGY IN BIOLOGICAL AND BIO-INSPIRED SYSTEMS

Organised by Dr Alex Chin (University of Cambridge), Professor Johnjoe McFadden (University of Surrey), Elisabeth Wallace (UK Science and Innovation Network)

Robinson College, University of Cambridge

Click here for the Workshop Programme!

Since its modern revival in 2007, the field of Quantum Effects in Biological Systems (QuEBS) has rapidly developed into a high profile interdisciplinary area of physical science, bringing together physicists, chemists and biologists to understand and explore the impact of quantum mechanics in some of the most important biological processes found in Nature.  Inspired by the new insights provided by QuEBS, the scope of inquiry is now expanding beyond the still unanswered questions of how and why quantum effects are protected in biomolecular structures.  This two-day workshop will investigate one of these exciting new questions; can QuEBS-like phenomena be artificially engineered for future (quantum) technologies?

The molecular architectures under study in QuEBS, and particularly those found in photosynthesis, are highly sophisticated, evolved solutions to a range of (biological) problems, and are exquisite examples of nanoscale engineering. While the possible role of quantum mechanics in enhancing efficiencies or robustness in these biological "devices" remains under debate, it is clear that any quantum enhancements operate in a fundamentally different mode compared to other quantum devices, such as quantum computers. Thus, from light harvesting in photosynthesis to avian navigation, natural phenomena provide conceptually new contexts to investigate how quantum effects can be protected and engineered for purpose. As many of the biological problems successfully tackled by Nature are also challenges faced by a range of current technologies, such as organic solar cells, catalysis and sensing, there is a growing opportunity to exploit the developing understanding of QuEBS outside of the biological domain. This potential has been recognized here in he UK, and we are delighted to acknowledge the support of the UK Science and Innovation Network in funding this workshop.

This meeting aims to bring together leading researchers in the area of QuEBS and related fields, hoping to facilitate a fruitful exchange of ideas, tools and expertise that may shape the possible development of bio-inspired quantum technologies and further our understanding of quantum effects in biological structure. By presenting the current state of knowledge in QuEBS, its experimental underpinnings, theoretical framework and major questions, we hope to show how developments in this area impact other disciplines, how it could breed novel types of bio-hybrid devices and also how other quantum technologies could provide valuable and detailed new information in this area.

 

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