School of Physics and Astronomy

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Prof Ben Varcoe

Theoretical Physics Group

Contact details

Room: 8.428 
Tel: +44 (0)113 3438290
Email: b.varcoe @ leeds.ac.uk

Keywords

Cavity Quantum Electrodynamics (Cavity QED)
Quantum Key Distribution (QKD)
Continuous Variable Quantum Key Distribution (CVQKD)
Medical Imaging
Quantum Imaging
Magnetocardiogaphy (MCG)

Research interests

Experimental Quantum Information

My principle research area is quantum information science where we are concerned with the physical nature of information and its manipulation. Information is not just a mathematically property, information has to be stored and processed. Storage is always a physical process and processing or manipulating the information requires a physical operation. For this reason information has to be a quantity that obeys the laws of physics. An understanding of the physics of information processing can help us find new ways of manipulating, storing and moving information. It therefore has widespread implications. To cite a specific example in magnetic medical imaging the largest problem faced by researchers was the removal of background noise. The signals, although small, are capable of being detected by a wide range of devices; hence, it is the treatment of the background which is the real problem. By understanding the nature of information we were able to devise a detection array in which the noise problem was dramatically reduced using an error correction mechanism drawn from quantum optics. Moreover we found that rather than reducing the noise, adding quantum noise actually enhances the ability to detect the signal. We also found that the entire signal processing path needs to be considered in the design of the apparatus, it is not sufficient to consider (or optimise) each element in isolation.

Quantum Communication

Experimental quantum communication at Leeds is working with a spinout company, Cryptographiq Limited, and development partners Airbus Defence and Space, and L3-TRL to develop new and novel communications technologies that will provide future proof cryptographic systems that are based on quantum information principles.

We are also working with the quantum communication hub to deliver a microwave quantum key distribution system. The quantum communications hub consortium has bid successfully for Government funding to be one of four hubs in the EPSRC's new £155m National Network of Quantum Technology Hubs announced today by Greg Clark, Minister of State for Universities, Science and Cities. The new hubs are the centre-piece of the £270 million investment in the UK National Quantum Technologies Programme announced by the Chancellor in the 2013 Autumn Statement.

Quantum Imaging

Coronary artery disease (CAD) represents a significant challenge to both cardiologists and emergency medicine specialists. They must diagnose both symptomatic and asymptomatic patients with multiple cardiovascular risk factors, as well as patients presenting with acute chest pain without any clinical signs. As of 2012, CAD was the most common cause of death globally and a major cause of hospital admissions. Acute coronary syndrome (ACS) refers to a spectrum of cardiac conditions ranging from unstable angina to myocardial infarction (MI) that are caused by a sudden reduction in blood flow to the heart. The most common symptom of ACS is chest pain. Distinguishing between ACS and other causes of chest pain is a huge challenge for cardiologists.

Medical Magnetocardiography (MCG), primarily using Superconducting Quantum Interference Devices (SQUIDs), has been used in clinical research for over 50 years, but its widespread adoption has been restricted by high costs (>1 million), the need for highly controlled environments and liquid helium cooling, as well as specialist staff. The University of Leeds has designed a portable magnetometer to enable MCG to be easily employed, at a reduced cost compared with SQUID MCG, in hospital accident and emergency departments or other acute settings.

The Magnetometer Model 1.0 (V1) is a prototype, which was developed using academic research funding at the University of Leeds. This is currently being used in a clinical study, which is also funded by a grant to the University. Quantum Imaging (QI) Ltd is developing Magnetometer Model 2.0 (V2), which can be easily deployed in an acute medical setting. Earlier this year Quantum Imaging Ltd was spun out from the University of Leeds to commercialise the technology.

The QI Magnetometer will identify healthy (non-cardiac) patients and as such addresses two significant unmet healthcare and clinical needs in cardiology. The first is to rule out CAD, including stable and unstable angina and MI, sooner in patients presenting with chest pain. Currently, only 13% of patients with chest pain are discharged within 4 hours of arrival; and around 75% of patients with chest pain of a non-cardiac origin are inappropriately triaged through the chest pain pathway. The second is to prevent inappropriate discharge of patients with a missed MI; around 2%-4% of patients with evolving MI are discharged from the emergency department because of normal electrocardiogram (ECG) findings.

This represents a step change in clinical capability. It will revolutionise the rapid diagnosis of CAD, filtering out those who do not need to be in the care a dedicated cardiology team quickly and efficiently. It will allow clinical teams to focus their effort on those patients who are most in need and reduce waiting times. This will lead to significant cost savings and improved health care.

Publications

Ghasemi-Roudsari S, Mooney JW, Reade Banham E, Symonds C, Pawlowski N, Varcoe BTH A portable diagnostic device for cardiac magnetic field mapping Biomedical Physics and Engineering Express 3 -, 2017
DOI:10.1088/2057-1976/3/1/015008
View abstract

Quinones DA, Varcoe B Decoherence in Excited Atoms by Low-Energy Scattering ATOMS 4 -, 2016
DOI:10.3390/atoms4040028

Thompson R, Varcoe B, Crawford A, Hatton P Lock-in amplified spontaneous Raman spectroscopy for calcium phosphates JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE 8 113-114, 2014

Everitt MS, Jones ML, Varcoe BTH Dephasing of entangled atoms as an improved test of quantized space time Journal of Physics B: Atomic, Molecular and Optical Physics 46 -, 2013
DOI:10.1088/0953-4075/46/22/224003
View abstract

Staples SGH, Vo C, Cowell DMJ, Freear S, Ives C, Varcoe BTH Solving the inverse problem of magnetisation-stress resolution JOURNAL OF APPLIED PHYSICS 113 -, 2013
DOI:10.1063/1.4799049

Johnson LAM, Majeed HO, Varcoe BTH A three-step laser stabilization scheme for excitation to Rydberg levels in Rb-85 APPLIED PHYSICS B-LASERS AND OPTICS 106 257-260, 2012
DOI:10.1007/s00340-011-4805-8

Jones ML, Sanguinetti B, Majeed HO, Varcoe BTH Evolutionary optimization of state selective field ionization for quantum computing APPL SOFT COMPUT 11 2079-2082, 2011
DOI:10.1016/j.asoc.2010.07.005

Everitt MS, Jones ML, Varcoe BTH, Dunningham JA Creating and observing N-partite entanglement with atoms J PHYS B-AT MOL OPT 44 -, 2011
DOI:10.1088/0953-4075/44/3/035504

Lovett NB, Varcoe BTH Generation of Topologically Useful Entangled States INTERNATIONAL JOURNAL OF UNCONVENTIONAL COMPUTING 7 273-289, 2011

Johnson LAM, Majeed HO, Varcoe BTH A three-step laser stabilization scheme for excitation to Rydberg levels in 85Rb Applied Physics B: Lasers and Optics 1-4, 2011

Johnson LAM, Majeed HO, Sanguinetti B, Becker T, Varcoe BTH Absolute frequency measurements of Rb-85 n F-7/2 Rydberg states using purely optical detection NEW J PHYS 12 -, 2010
DOI:10.1088/1367-2630/12/6/063028

Sanguinetti B, Majeed HO, Jones ML, Varcoe BTH Precision measurements of quantum defects in the nP(3/2) Rydberg states of Rb-85 J PHYS B-AT MOL OPT 42 -, 2009
DOI:10.1088/0953-4075/42/16/165004

Jones ML, Wilkes GJ, Varcoe BTH Single microwave photon detection in the micromaser J PHYS B-AT MOL OPT 42 -, 2009
DOI:10.1088/0953-4075/42/14/145501

Blackman MR, Varcoe BTH MAGNETOMETRY USING ELECTROMAGNETICALLY INDUCED TRANSPARENCY IN A ROOM TEMPERATURE VAPOUR CELL Developing an Optical Magnetometer that Utilises the Steep Dispersion Curve Observed in EIT to Detect Time Varying Magnetic Fields, 2009

Everitt M, Dunningham J, Varcoe BTH Quantum computing with rydberg atoms in cavities, 2009

Cotter JP, Hill MP, Varcoe BTH Probing Lorentz invariance using coherent optical phenomena Proceedings of the 4th Meeting on CPT and Lorentz Symmetry, CPT 2007 287-289, 2008
View abstract

Blythe PJ, Varcoe BTH A cavity-QED scheme for cluster-state quantum computing using crossed atomic beams New Journal of Physics 8 pp.231-, 2006
DOI:10.1088/1367-2630/8/10/231

Sanguinetti B, Varcoe BTH Use of a piezoelectric SQUIGGLE (R) motor for positioning at 6 K in a cryostat CRYOGENICS 46 694-696, 2006
DOI:10.1016/j.cryogenics.2006.02.007

Walther H, Varcoe BTH, Englert BG, Becker T Cavity quantum electrodynamics REP PROG PHYS 69 1325-1382, 2006
DOI:10.1088/0034-4885/69/5/R02

Varcoe BTH Testing special relativity using slow light CONTEMP PHYS 47 25-32, 2006
DOI:10.1080/00107510500389176

Varcoe BTH, Brattke S, Walther H The creation and detection of arbitrary photon number states using cavity QED, 2004
DOI:10.1088/1367-2630/6/1/097

Varcoe BTH, Brattke S, Walther H The creation and detection of arbitrary photon number states using cavity QED New Journal of Physics 6 1-22, 2004
DOI:10.1088/1367-2630/6/1/097
View abstract

Walther H, Brattke S, Varcoe BTH, Becker T, Marchi G, Urbonas L Measurement of number states and phase diffusion using the micromaser Journal of Modern Optics 51 933-943, 2004
View abstract

Varcoe BTH Quantum states in a one atom maser OSA Trends in Optics and Photonics Series 97 207-209, 2004
View abstract

Brattke S, Guthohrlein GR, Keller M, Lange W, Varcoe B, Walther H Generation of photon number states on demand, 2003
DOI:10.1080/0950034031000064889

Brattke S, Guthohrlein GR, Keller M, Lange W, Varcoe B, Walther H Generation and investigation of number states of the radiation field LASER PHYS 13 368-374, 2003

Varcoe BTH Generation of non-classical states of light using highly excited atoms, 2003
DOI:10.1109/EQEC.2003.1314169
View abstract

Brattke S, Varcoe BTH, Walther H Generation of Photon Number States on Demand via Cavity Quantum Electrodynamics Physical Review Letters 86 3534-3537, 2001
DOI:10.1103/PhysRevLett.86.3534

Varcoe BTH, Sang RT, MacGillivray WR, Standage MC Quantum state reconstruction using atom optics PHYS REV A 6304 -, 2001

Sang RT, Summy GS, Varcoe BTH, MacGillivray WR, Standage MC Internal-quantum-state engineering using magnetic fields PHYS REV A 6302 -, 2001

Brattke S, Varcoe BTH, Walther H Preparing Fock states in the micromaser OPT EXPRESS 8 131-144, 2001
View abstract

Bartlett SD, Sanders BC, Varcoe BTH, De Guise H Quantum computation with harmonic oscillators, 2001
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Varcoe BTH, Sang RT, MacGillivray WR, Standage MC Quantum state reconstruction using atom optics Physical Review A. Atomic, Molecular, and Optical Physics 63 414011-414014, 2001

Sang RT, Summy GS, Varcoe BTH, MacGillivray WR, Standage MC Internal-quantum-state engineering using magnetic fields Physical Review A - Atomic, Molecular, and Optical Physics 63 1-9, 2001
DOI:10.1103/PhysRevA.63.023408
View abstract

Varcoe BTH, Sang RT, MacGillivray WR, Standage MC Quantum state reconstruction using atom optics Physical Review A - Atomic, Molecular, and Optical Physics 63 1-4, 2001
DOI:10.1103/PhysRevA.63.041401
View abstract