Towards enhanced interferometry using quantum states of light

On Wednesday 17th of October we had the pleasure to welcome Dr. Chris Wade from Oxford University to give a seminar to the AMOPP group about progress towards interferometry with exotic quantum states of light, more specifically Holland-Burnett states. This was a very interesting talk with a great mix of theory and experimental results. The abstract can be seen below.

Towards enhanced interferometry using quantum states of light

Quantum metrology is concerned with the enhanced measurement precision that may be gained by exploiting quantum mechanical correlations. In the scenario presented by optical inteferometry, several successful implementations have already been demonstrated including gravitational wave detectors [1], and lab-scale experiments [2,3]. However there are still open problems to be solved, including loss tolerance and scalability. In this seminar I will present progress implementing loss-tolerant Holland-Burnett states [4], and work searching for other practical states to implement [5].

[1] Schnabel et al. Nat. Comm. 1. 121 (2010)
[2] Slussarenko et al. Nat. Phot. 11, 700 (2017)
[3] Yonezawa et al. Science, 337, 1514 (2012)
[4] Holland and Burnett, PRL, 71, 1355 (1993)
[5] Knott et al, PRA, 93, 033859 (2016)

The Measurement Postulates of Quantum Mechanics are Redundant

On Wednesday 10th October we had Dr. Luis  Masanes from within the UCL AMOPP group give a very interesting seminar. His talk was focused on the fundamental questions posed by the measurement postulates of quantum mechanics, and how they are redundant given the other postulates that form the basis of quantum mechanics. Dr. Masanes was kind enough to provide a copy of his slides here and the abstract can be seen below.

The Measurement Postulates of Quantum Mechanics are Redundant

Understanding the core content of quantum mechanics requires us to disentangle the hidden logical relationships between the postulates of this theory. The theorem presented in this work shows that the mathematical structure of quantum measurements, the formula for assigning outcome probabilities (Born’s rule) and the post-measurement state-update rule, can be deduced from the other quantum postulates, often referred to as “unitary quantum mechanics”. This result unveils a deep connection between the dynamical and probabilistic parts of quantum mechanics, and it brings us one step closer to understand what is this theory telling us about the inner workings of Nature.

Levitated Quantum Nanophotonics

On Wednesday 1st November we had Professor Lukas Novotny from the Photonics Laboratory in ETH, Zürich give an insightful AMOPP seminar. His expertise spans many  areas, from optical antennas, near-field optics, nonlinear plasmonics and more. However, during his talk he focused on nanoparticle trapping and cooilng. The abstract for his talk can be found below, and he agreed to provide a copy of his slides which you can download here.

Abstract:

Levitated Quantum Nanophotonics
Vijay Jain [a], Martin Frimmer [a], Erik Hebestreit [a], Jan Gieseler[a], Romain Quidant [b], Christoph Dellago [c], and Lukas Novotny [a]
a) ETH Zurich, Photonics Laboratory, 8093 Zurich, Switzerland.
b) ICFO, Mediterranean Technology Park, 08860 Castelldefels, Spain.
c) University of Vienna, Faculty of Physics, 1090 Vienna, Austria.

I discuss our experiments with optically levitated nanoparticles in ultrahigh vacuum. Using active parametric feedback we cool the particle’s center-of-mass temperature to T = 100μK and reach mean quantum occupation numbers of n = 15. I show that mechanical quality factors of Q = 109 can be reached and that damping is dominated by photon recoil heating. The vacuum-trapped nanoparticle forms an ideal model system for studying non-equilibrium processes, nonlinear interactions, and ultrasmall forces.

Towards endoscopic magnetic field sensors for biomedical applications

On Wednesday 25th of October, we had our weekly AMOPP seminar by Dr. Arne Wickenbrock from the Budker Group at the Helmholtz Institute of Johannes Gutenberg-University in Mainz, Germany. His research spans a wide range of fields including dark matter and dark energy constituents (GNOMECASPEr), zero- and ultralow-field nuclear magnetic resonance (ZULF-NMR) and many more. But this time his talk was actually focused on using Nitrogen-Vacancy centers in diamond as a means of detection for small magnetic fields, in the hopes of being able to use this as a medical diagnosis technique in the near future. The abstract for his talk can be found below.

Abstract:

Towards endoscopic magnetic field sensors for
biomedical applications
Arne Wickenbrock1,2, Georgios Chatzidrosos1, Huijie Zheng1, Lykourgos Bougas1, Dmitry
Budker1,2,3
1Johannes Gutenberg-University, Mainz, Germany,
2Helmholtz Institut Mainz, Mainz, Germany,
3Department of Physics, University of California, Berkeley, CA 94720-7300, USA
 
We propose and report on the progress towards a miniaturized endoscopic magnetic field sensor based on color center ensembles in diamond. The unique design of the sensor enables spatially resolved in-vivo measurements of static and oscillating magnetic fields with a broad bandwidth and high sensitivity. An endoscopic magnetometer could boost the size of magnetic signals of the heart, the brain or other organs due to the reduced distance to the underlying current densities. The high-bandwidth of the device enables spatially resolved methods for tissue discrimination such as nuclear magnetic resonance or eddy-current detection in vivo.  
An endoscopic sensor motivates two simultaneous approaches, firstly, we present a highly sensitive magnetometer that measures magnetic fields by monitoring cavity-enhanced absorption on the singlet transition of the negatively charged nitrogen-vacancy (NV) center in diamond under radio-frequency irradiation and optical pumping with a green laser. We achieve shot-noise limited performance with sensitivities better than 30 pT/Hz1/2 [1].
Secondly, the rapidly changing environment in the human body as well as exposure limits for electromagnetic radiation motivate the use of a microwave-free magnetometer. We demonstrated such a device based on a narrow magnetic feature due to the ground-state level anticrossing (GSLAC) of the NV center at a background field of 102 mT to measure magnetic fields without microwaves [2]. Additionally, we plan to combine the NV center magnetometer with a much more sensitive alkali vapor cell magnetometer to build a novel brain-machine interface at room temperature and in an unshielded environment. 
 
[1] G. Chatzidrosos, A. Wickenbrock, L. Bougas, N. Leefer, T. Wu, K. Jensen, Y. Dumeige, and D. Budker, Miniature cavity-enhanced diamond magnetometer, in preparation, 2017.
[2] A. Wickenbrock, H. Zheng, L. Bougas, N. Leefer, S. Afach, A. Jarmola, V. M. Acosta, and D. Budker, Microwave-free magnetometry with nitrogenvacancy centers in diamond, Applied Physics Letters 109, 053505 (2016)
[3] H. Zheng, G. Chatzidrosos, A. Wickenbrock, L. Bougas, R. Lazda, A. Berzins, F. H.Gahbauer, M. Auzinsh, R. Ferber, and D. Budker, Level anticrossing magnetometry with color centers in diamond, Proc. of SPIE Vol. 10119 101190X-1, 2017.

Taming polar molecules for quantum experiments

On Wednesday 11th of October our weekly AMOPP seminar was given by Dr. Martin Zeppenfeld from the Rempe Group at the Max Planck institute for quantum optics in Garching, Germany. His talk focused on their experiments involving the manipulation of cold polar molecules which Dr. Zeppenfeld leads. You can visit their website to find out more about their research, and the abstract for his talk is given below.

Abstract:

Polar molecules offer fascinating opportunities for quantum experiments at cold and ultracold temperatures. For example, chemistry at low temperatures features new possibilities such as controlling chemical reactions via electric and magnetic fields or observing reactions based on tunneling through a reaction barrier. Precision measurements on molecules provide insight into fundamental physics, allowing investigation of physics beyond the standard model. Attaining sufficient control over molecules provides opportunities for quantum simulations and quantum information processing.

In my talk I will present two aspects of our work on polar molecules. First, I will present our toolbox of techniques to produce molecule ensembles at very low temperatures. This includes centrifuge deceleration of cryogenic-buffer-gas cooled molecular beams as well as optoelectrical Sisyphus cooling of formaldehyde to sub-millikelvin temperatures. Second, I will present our progress towards quantum experiments coupling polar molecules to Rydberg atoms. As a first step, we have investigated electric field controlled collisions between polar molecules.

Optical spectroscopy for nuclear and atomic science at JYFL, Finland

On Wednesday 4th of October, we had the privilege of having Professor Iain D. Moore from the University of Jyväskylä as an invited speaker for one of our AMOPP seminars. The seminar focused mainly on the work they have been doing at the various accelerator facilities at JYFL and had a good mix of nuclear and atomic physics content.

Professor Iain D. Moore kindly agreed to provide a copy of his presentation slides which you can download here.

Abstract:

Optical spectroscopy for nuclear and atomic science at JYFL, Finland

Iain D. Moore, University of Jyväskylä

 

High-resolution optical measurements of the atomic level structure readily yield fundamental and model-independent data on nuclear ground and isomeric states, namely changes in the size and shape of the nucleus, as well as the nuclear spin and electromagnetic moments [1]. Laser spectroscopy combined with on-line isotope separators and novel ion manipulation techniques provides the only mechanism for such studies in exotic nuclear systems.

Internationally, there are a myriad of tools in use however these are traditionally variants of two main workhorses in the field – collinear laser spectroscopy and resonance ionization spectroscopy. Following a short overview of the Accelerator Laboratory at the University of Jyväskylä, I will briefly present both techniques and their use in accessing the heavy element region of the nuclear landscape which exhibits rather scarce information from optical studies. This reflects a combination of the difficulty in producing such elements (low production cross sections) and a lack of stable isotopes (thus few optical transitions available in literature). Indeed, this past year has seen a number of exciting developments including optical studies of exotic atoms produced at the level of one atom-at-a-time [2], and high-resolution spectroscopy in supersonic gas expansions [3].

Recently, we have initiated a new program on the actinide elements in collaboration with the University of Mainz. I will summarize the current status of the work which includes collinear laser spectroscopy on Pu, the heaviest element attempted with this particular technique [4]. Our focus has recently turned to the study of the lowest-lying isomeric state in the nuclear chart, 229Th.  Almost 40 years of research has been invested into efforts to observe the isomeric transition which, if found, may be directly accessed by lasers. In 2016, the community was given a tremendous boost with the unambiguous identification of the state by a group in Munich, providing a stepping stone towards a future realization of a “nuclear clock” [5].

[1] P. Campbell, I.D. Moore and M.R. Pearson, Progress in Part. and Nucl. Phys. 86 (2016) 127.

[2] M. Laataioui et al., Nature 538 (2016) 495.

[3] R. Ferrer et al., Nature Communications 8 (2017) 14520.

[4] A. Voss et al., Phys. Rev. A 95 (2017) 032506.

[5] L. von der Wense et al., Nature 533 (2016) 47.

Eberhard Widman, In-beam hyperfine spectroscopy of (anti)hydrogen

20170222_160853

On Wednesday 22nd of February, we had the pleasure of to host Professor Eberhard Widman as one of our weekly invited speakers for AMOPP seminars.  His research in the ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration is heavily related to the kind of antimatter experiments that we do at UCL, except they deal with anti-hydrogen atoms which they produce using positrons and anti-protons from the Antiproton Decelerator (AD) at CERN. The main focus of his talk was the prospect of making measurements of the hyperfine structure of anti-hydrogen.

He kindly agreed to provide a copy of his slides, which you can download  here.

Abstract:

In-beam hyperfine spectroscopy of (anti)hydrogen

Prof. Dr. Eberhard Widmann, Director, Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences Boltzmanngasse 3, A-1090 Wien

The ground-state hyperfine structure (GS-HFS) of hydrogen is known from the hydrogen maser to relative precision of 10–12. It is of great interest to measure the same quantity for its antimatter counterpart, antihydrogen, to test the fundamental CPT symmetry, which states that all particles and antiparticles have exactly equal or exactly opposite properties. Since CPT is strictly conserved in the Standard Model of particle physics, a violation, if found, would point directly to theories behind this framework. The application of the maser technique requires the confinement of the atoms in a matter box for 1000 seconds and is currently not applicable to antihydrogen. Therefore, the ASACUSA collaboration at the Antiproton Decelerator of CERN has built a Rabi-type beam spectroscopy setup for a measurement of GS-HFS.

With the initial aim of characterizing the setup devised to measure the GS-HFS and to evaluate its potential, a beam of cold, polarized, monoatomic hydrogen was built and used together with the microwave cavity and sextupole magnet designed for the antihydrogen experiment. The (F,M)=(1,0) to (0,0) transition was measured to a precision of several ppb [1], more than a factor 10 better than in the previous measurement using a hydrogen beam. This result shows that the apparatus developed is capable of making a precise measurement of the GS-HFS of antihydrogen provided a beam of similar characteristics (velocity, polarization, quantum state) becomes available.

In a recent publication on the non-minimal Standard Model Extension (SME), describing possible violations of Lorentz and CPT invariance, Kostelecky and Vargas [2] conclude that the in-beam hyperfine measurements of hydrogen alone can be used to constrain certain coefficients of their model, which have never been measured before. The status and prospects of in-beam measurements of hydrogen and antihydrogen will be presented.

[1] M. Diermaier et al., arxiv : 1610.06392

[2] V.A. Kostelecky and A.J. Vargas, Physical Review D 92, 056002 (2015).