Durham Atomic and Molecular Physics 
AtMol Research Seminar Archive

Date  Speaker  Institution 

Ion trapping  
21st September  Prof. Christopher Monroe  University of Maryland 
This was an exceptional seminar on work by the group of Prof. Monroe on Ion trapping.


No seminar  
13th October  


Precision frequency metrology (cancelled)  
20th October  Prof. Ben Varcoe  University of Leeds 
In this talk I will present a line of work that we have been following for the last few years in the development of a system for absolute frequency metrology of atomic lines. The rubidium Rydberg series is the system that we have used as a focal point of our effort, primarily because of its importance to microwave cavity QED and for our experiments in special and general relativity. In developing this system we have found a number of inconsistencies and gaps in the field that we have been able to reconcile, such as a 10 standard deviation difference between two recent measurements of the D1 line and resolving a long standing error in D2 line spectroscopy. We use a combination of a three laser excitation scheme and microwave spectroscopy linked to a GPS disciplined atomic clock and a 250MHz frequency comb. The comb system was tailor made for our application and provides reference light spanning two octaves from 500nm to 2000nm. The system that we have created is capable of performing precision spectroscopy on the Rydberg series, ns, np, nd, nf, ng and nh. Our most recent result is an observation of van der Waals interactions between 5s ground states and np and nf excited states.


From ultracold to ultrahot: quasirelativistic dynamics in atomic quantum gases  
27th October  Dr Patrik Öhberg  HeriotWatt University 
Artificial electromagnetism is a new tool to manipulate charge neutral quantum gases. In this talk we will look at how spinorbit coupling arises in these gases and how it can be used to simulate quasirelativistic dynamics and find connections to phenomena known from high energy physics.


Journal Club talk: David Holdaway  
3rd November  Mr David Holdaway  Durham University 
Photosynthesis provides the base nutrients for almost all life on earth, recent experimental and theoretical work on the phenomina has yielded interesting results, suggesting that long lived quantum coherence can be found in light harvesting protein "antenna" is used as a mechanism to transfer excitation energy to reaction center even at room temperature.
This talk focuses on the experimental techniques of three pulse two photon echo (2PE) spectroscopy and the results obtained in the paper "Coherently wired lightharvesting in photosynthetic marine algae at ambient temperature" E. Collini, C. Y. Wong et al, doi:10.1038/nature08811


Manipulating and probing microwave fields in a cavity by quantum nondemolition photon counting  
10th November  Dr Michel Brune  École normale supérieure  Paris 
We perform quantum nondemolition photon (QND) counting in a high Q cavity. Microwave photons are stored in a superconducting cavity for time as long as 0.1s. By using Rydberg atoms as clocks whose ticking rate is affected by light shifts induced by the cavity field, we realize an ideal projective measurement of the photon number. The experiment demonstrates all features of quantum measurement theory: random results, state projection and repeatabily.
Measuring the atoms is an efficient way for preparing by projection nonclassical states such as number states or Schrödinger cat states. We use the QND measurement method for reconstructing the Wigner function of these states and to monitor their decoherence. These field manipulation methods can be applied to state preparation by quantum feedback and to demonstrate nonlocality with two fields located in separated cavities.


Hybrid quantum computing with spin ensembles and super conducting qubits  
17th November (Lunch time 13:0014:00)  Prof. Klaus Mølmer  Aarhus University 
In conventional registers for quantum information processing, quantum bits are associated with individual twolevel quantum systems. Separate addressing and interaction with these systems permit onebit gates, while an interaction between systems is needed to accomplish twobit gates. I will review a recent proposal to implement quantum computing in collective excitation degrees of freedom in ensembles of identical quantum systems.
In this proposal one does not need to address individual particles, but one needs an interaction between all particles in the system. Such interactions exist in hybrid systems where large spinensembles are coupled to superconducting qubit elements via a resonant single mode of the quantized radiation field. We will review the main ideas of ensemble encoding and we will discuss recent results on the effects of unwanted interactions and inhomogeneities in such systems.


Nanoelectromechanical Systems in the Quantum Regime  
17th November  As Prof. Andrew Armour  University of Nottingham 


Bose Einstein condensates of Chromium  
24th November  Dr Bruno LaburtheTolra  Laboratoire de Physique des Lasers 


Optical Trapping and Manipulation of Nanostructures  
1st Decemember  Dr Phil Jones  University College London 
In this talk I will present recent work from the UCL Optical Tweezers Group on the application of optical trapping methods to the nanoscale. I will start by describing the working of the singlebeam laser trap or optical tweezers and the limitations encountered when trying to trap nanoparticles, before discussing the application to nanomaterials such as gold nanorods, carbon nanotubes, graphene flakes and polymer nanowires.
Our experiments with these objects include measurement of optically induced rotations and force measurements in the femtoNewton regime. I will then go on to discuss how novel beamshaping techniques can be applied to optical tweezers that could lead to improved trapping of nanoparticles, before presenting our most recent activity aimed at using lightcarrying nanostructures for optical trapping and manipulation


Journal club talk: Magnetically Trapped Antihydrogen  
8th Decemember  Mr Lee Weller  Durham University 
Based on the paper G. B. Andresen et al. Nature 468, 673–676 (02 December 2010). Antimatter was first predicted1 in 1931, by Dirac. Work with highenergy antiparticles is now commonplace, and antielectrons are used regularly in the medical technique of positron emission tomography scanning. Antihydrogen, the boundstate of an antiproton and a positron, has been produced2, 3 at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature's fundamental symmetries. The charge conjugation/parity/time reversal (CPT) theorem, a crucial part of the foundation of the standard model of elementary particles and interactions, demands that hydrogen and antihydrogen have the same spectrum. Given the current experimental precision of measurements on the hydrogen atom (about two parts in 1014 for the frequency of the 1sto2s transition4), subjecting antihydrogen to rigorous spectroscopic examination would constitute a compelling, modelindependent test of CPT.
Antihydrogen could also be used to study the gravitational behaviour of antimatter5. However,so far experiments have produced antihydrogen that is not confined, precluding detailed study of its structure. Here we demonstrate trapping of antihydrogen atoms. From the interaction of about 107 antiprotons and 7×108 positrons, weobserved 38 annihilation events consistent with the controlled release of trapped antihydrogen from our magnetic trap; the measured background is 1.4±1.4 events. This result opens the door to precision measurements on antiatoms, which can soon be subjected to the same techniques as developed for hydrogen.


Journal club talk: Quantum Random Walks  
15th December  Mr Chris Carr  Durham University 
In my journal club talk, I will review recent work by Jeremy O'Brien at the University of Bristol. O'Brien has shown that lattices of coupled waveguides are an extremely versatile tool that can be used to manipulate the flow of light. The photons undergo random walks in the waveguide lattice and develop nontrivial quantum correlations. Such a system also enables direct observation of optical analogues of many fundamental quantum mechanical effects. Following a review of the applications of random walk analysis, I will look at how classical and random walks are different. A brief encounter with some basic quantum optics will then be followed by a presentation of the experimental results from the waveguide lattice.
