Author Archives: wvk_sm9je57j

Collimation of laser beams from optical fibers

An ESA milestone reached.

Our ESA Space-Optics project has reached a major milestone:  We have finished the development of a novel beam collimation technique, which works allows us to adjust the waist of the laser beam emitted from a fibre coupler to an arbitrary position simply by maximising the peak intensity of the laser beam at some other position.

ZERODUR collimator

This is a fiber collimator manufactured from the ultra-low expansion material ZERODUR.

In order to make the coupler space-compatible it is manufactured from ultra-low-expansion ceramics (ZERODUR) and has no moving parts.

Quantum Technologies in Space (QTSpace)

We have been appointed the Greek representatives of “Quantum Technologies in Space (QTSpace)”.

The scientific and technological legacy of the 20th century includes milestones such as quantum mechanics and pioneering space missions. Both endeavours have opened new avenues for the furthering of our understanding of Nature, and are true landmarks of modern science. Quantum theory and space science form building blocks of a powerful research framework for exploring the boundaries of modern physicsthrough the unique working conditions offered by experimental tests performed in space.

Space-based sources of entangled photons promise the formation of global quantum communication networks, long-distance tests of quantum theory and the interplay between relativity and quantum entanglement.

 

Long free-fall times enable high-precision tests of general relativity and tests of the equivalence principle for quantum systems.

Harnessing microgravity, high vacuum and low temperature of deep space promises allowing the study of deviations from standard quantum theoryfor high-mass test particles. Space-based experiments of metrology and sensing will push the precision of clocks, mass detectors and transducers towards the engineering of novel quantum technologies.

Matter-wave interferometers using TAAP rings

New Journal of Physics   18   075014 (2016)

P. Navez, S. Pandey, H. Mas, K. Poulios, T. Fernholz, and W. von Klitzing

doi: 10.1088/1367-2630/18/7/075014

Fig 2

Figure 2. Experimental realisation of a ring-shaped TAAP waveguide. The radius of the ring is R = 570 μm.

Abstract: We present two novel matter-wave Sagnac interferometers based on ring-shaped time-averaged adiabatic potentials, where the atoms are put into a superposition of two different spin states and manipulated independently using elliptically polarized rf-fields. In the first interferometer the atoms are accelerated by spin-state-dependent forces and then travel around the ring in a matter-wave guide. In the second one the atoms are fully trapped during the entire interferometric sequence and are moved around the ring in two spin-state-dependent `buckets’.

Figure 6.

Figure 6. Experimental realisation of arbitrary traps. The fitted radius is 440 μm and 450 μm respectively.  Note that (a) and (b) are taken with identical experimental conditions and differ only in the state of the atoms. The axis of the circular rf component and the one of the tilted modulation are not orthogonal.

Corrections to the ideal Sagnac phase are investigated for both cases. We experimentally demonstrate the key atom-optical elements of the interferometer such as the independent manipulation of two different spin states in the ring-shaped potentials under identical experimental conditions.

Georgios Vasilakis

Welcome back Georgos !

Georgos Vasilakis is joining us as a postdoc on BEC1.

Before joining us Vasilis was…

09/2012 – 04/2016 PostDoc at the Niels Bohr Institute, Copenhagen
Georgo was a Post-Doctoral Research Associate in the Quantop Group
of Eugene S. Polzik  at the Niels Bohr Institute, University of Copenhagen.  He was working on Experimental quantum optics / Light-atom quantum interface.
04/2006 – 03/2016 PhD at Princeton University
Georgos did his PhD and M.S. at  Princeton University, NJ under the supervision of  Professor Michael V. Romalis.  The topic of his PhD thesis was: “Precision Measurements of Spin Interactions with High Density Atomic Vapors”

Adiabatic Potentials and Atom Lasers

Rom. Rep. Phys. 67 295 (2015). (link)

V. Bolpasi and W. von Klitzing

Abstract: 
The brightest atom lasers to date are formed by time-dependent adiabatic potentials from magnetic Ioffe-Pritchard traps. We analyse these potentials based on a harmonic trap in the presence of gravity. We present a detailed analytic model of the trap and determine the flux of the atom laser, which we find to be in good agreement with recent experimental data. We also present a novel method for determining the Rabi frequency of the dressing rf-field.

Design of a dual species atom interferometer for space

Experimental Astronomy 39:2 167-206 (2015) (link)  (arXive)
Thilo Schuldt et al.Abstract:
Atom interferometers have a multitude of proposed applications in space including precise measurements of the Earth’s gravitational field, in navigation & ranging, and in fundamental physics such as tests of the weak equivalence principle (WEP) and gravitational wave detection. While atom interferometers are realized routinely in ground-based laboratories, current efforts aim at the development of a space compatible design optimized with respect to dimensions, weight, power consumption, mechanical robustness and radiation hardness. In this paper, we present a design of a high-sensitivity differential dual species 85Rb/87Rb atom interferometer for space, including physics package, laser system, electronics and software. The physics package comprises the atom source consisting of dispensers and a 2D magneto- optical trap (MOT), the science chamber with a 3D-MOT, a magnetic trap based on an atom chip and an optical dipole trap (ODT) used for Bose-Einstein condensate (BEC) creation and interferometry, the detection unit, the vascuum system for 10-11 mbar ultra-high vacuum generation, and the high-suppression factor magnetic shielding as well as the thermal control system. The laser system is based on a hybrid approach using fiber-based telecom components and high-power laser diode technology and includes all laser sources for 2D-MOT, 3D-MOT, ODT, interferometry and detection. Manipulation and switching of the laser beams is carried out on an optical bench using Zerodur bonding technology. The instrument consists of 9 units with an overall mass of 221 kg, an average power consumption of 608 W (819 W peak), and a volume of 470 liters which would well fit on a satellite to be launched with a Soyuz rocket, as system studies have shown.

An ultra-bright atom laser

The article has selected the article as a New Journal of Physics Highlight of the year 2014.

Phys.org has published a nice semi-popular article about the paper. The New Scientist has also written a rather popularized article about our atom laser.
Note that we have not been given access to any of these articles before publication and are not responsible for its rather imaginative content.

   

An article in Greek can be found in a number of newspapers, e.g. at Kerdos.gr and in.gr
Article at Kerdos and  Article at In.gr

Sigma Live also have made a video interview in Greek about the atom laser.

Fundamentals of cavity-enhanced polarimetry for parity-nonconserving optical rotation measurements: Application to Xe, Hg, and I

Physical Review A   89   052127 (2014)

L. Bougas, G. E. Katsoprinakis, W. von Klitzing, and T. Rakitzis

http://dx.doi.org/10.1103/PhysRevA.89.052127   or   https://journals.aps.org/pra/abstract/10.1103/PhysRevA.89.052127

Abstract: We present the theoretical basis of a cavity-enhanced polarimetric scheme for the measurement of parity-nonconserving (PNC) optical rotation. We discuss the possibility of detecting PNC optical rotation in accessible transitions in metastable Xe and Hg, and ground state I. In particular, the physics of the PNC optical rotation is presented, and we explore the lineshape effects on the expected PNC optical rotation signals. Furthermore, we present an analysis of the eigenpolarizations of the cavity-enhanced polarimeter, which is necessary for understanding the measurement procedure and the ability of employing robust background subtraction procedures using two novel signal reversals. Using recent atomic structure theoretical calculations, we present simulations of the PNC optical rotation signals for all proposed transitions, assuming a range of experimentally feasible parameters. Finally, the possibility of performing sensitive measurements of the nuclear-spin-dependent PNC effects is investigated, for the odd-neutron nuclei 129Xe and 199Hg, and the odd-proton nucleus 127I.

 

 Cavity frequency polarization spectrum. For the simulations we used θF =13 mad and δ = θF/2 = 6.5 mad and for demonstration purposes φPNC = 0.6 mad. (i) The Faraday effect splits the cavity spectrum into R and L modes by 2ωF = 2θF(c/L) (twofold degeneracy); (ii) the PNC optical rotation splits further the clockwise (CW) and counterclockwise (CCW) modes by 2ωPNC = 2φPNC(c/L), while the cavity modes remain circular polarization states; (iii) in the presence of linear birefringence (δ ̸= 0) the frequency splitting of the eigenmodes increases as ωF′ = 1/qωF and the measured PNC- induced splitting is reduced ωF′ = qωF (0 ≤ q ≤ 1) (see Fig. 3); the eigenmodes transform into elliptical states as observed from the different amplitudes of the output light (see the text for discussion). We also assume that the clockwise input beam was p polarized, while the counterclockwise beam was s polarized. The cavity’s linewidth is exaggerated for demonstration purposes; note that the free spectral range of the cavity is ωFSR = 2π × 40 MHz. In (i)–(iii), the gray dashed line corresponds to the fourfold degenerate axial mode of an isotropic cavity. PBS stands for polarizing beam splitter and BS stands for beam splitter.

Cavity frequency polarization spectrum. For the simulations we used θF =13 mad and δ = θF/2 = 6.5 mad and for demonstration purposes φPNC = 0.6 mad. (i) The Faraday effect splits the cavity spectrum into R and L modes by 2ωF = 2θF(c/L) (twofold degeneracy); (ii) the PNC optical rotation splits further the clockwise (CW) and counterclockwise (CCW) modes by 2ωPNC = 2φPNC(c/L), while the cavity modes remain circular polarization states; (iii) in the presence of linear birefringence (δ ̸= 0) the frequency splitting of the eigenmodes increases as ωF′ = 1/qωF and the measured PNC- induced splitting is reduced ωF′ = qωF (0 ≤ q ≤ 1) (see Fig. 3); the eigenmodes transform into elliptical states as observed from the different amplitudes of the output light (see the text for discussion). We also assume that the clockwise input beam was p polarized, while the counterclockwise beam was s polarized. The cavity’s linewidth is exaggerated for demonstration purposes; note that the free spectral range of the cavity is ωFSR = 2π × 40 MHz. In (i)–(iii), the gray dashed line corresponds to the fourfold degenerate axial mode of an isotropic cavity. PBS stands for polarizing beam splitter and BS stands for beam splitter.