Imperial College London

Dr Sauer

Faculty of Natural SciencesDepartment of Physics

Professor of Physics
 
 
 
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Contact

 

+44 (0)20 7594 7868ben.sauer Website

 
 
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Assistant

 

Miss Sanja Maricic +44 (0)20 7594 7742

 
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Location

 

212Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

69 results found

Caldwell L, Devlin J, Williams H, Fitch N, Hinds E, Sauer B, Tarbutt Met al., Deep laser cooling and effcient magnetic compression of molecules, Physical Review Letters, ISSN: 0031-9007

We introduce a scheme for deep laser cooling of molecules based on robust dark states at zero velocity. By simulating this scheme, we show it to be a widely applicable method that can reach the recoil limit or below. We demonstrate and characterise the method experimentally, reachinga temperature of 5.4(7) μK. We solve a general problem of measuring low temperatures for large clouds by rotating the phase-space distribution and then directly imaging the complete velocity distribution. Using the same phase-space rotation method, we rapidly compress the cloud. Applying the cooling method a second time, we compress both the position and velocity distributions.

Journal article

Cournol A, Manceau M, Pierens M, Lecordier L, Tran DBA, Santagata R, Argence B, Goncharov A, Lopez O, Abgrall M, Le Coq Y, Le Targat R, Martinez HA, Lee WK, Xu D, Pottie P-E, Hendricks RJ, Wall TE, Bieniewska JM, Sauer BE, Tarbutt MR, Amy-Klein A, Tokunaga SK, Darquie Bet al., 2019, A new experiment to test parity symmetry in cold chiral molecules using vibrational spectroscopy, QUANTUM ELECTRONICS, Vol: 49, Pages: 288-292, ISSN: 1063-7818

Journal article

Blackmore JA, Caldwell L, Gregory PD, Bridge EM, Sawant R, Aldegunde J, Mur-Petit J, Jaksch D, Hutson JM, Sauer BE, Tarbutt MR, Cornish SLet al., 2019, Ultracold molecules for quantum simulation: rotational coherences in CaF and RbCs, Quantum Science and Technology, Vol: 4, ISSN: 2058-9565

Polar molecules offer a new platform for quantum simulation of systems with long-range interactions, based on the electrostatic interaction between their electric dipole moments. Here, we report the development of coherent quantum state control using microwave fields in 40Ca19F and 87Rb133Cs molecules, a crucial ingredient for many quantum simulation applications. We perform Ramsey interferometry measurements with fringe spacings of ~1 kHz and investigate the dephasing time of a superposition of N = 0 and N = 1 rotational states when the molecules are confined. For both molecules, we show that a judicious choice of molecular hyperfine states minimises the impact of spatially varying transition-frequency shifts across the trap. For magnetically trapped 40Ca19F we use a magnetically insensitive transition and observe a coherence time of 0.61(3) ms. For optically trapped 87Rb133Cs we exploit an avoided crossing in the AC Stark shifts and observe a maximum coherence time of 0.75(6) ms.

Journal article

Jarvis K, Sauer B, Tarbutt M, 2018, Characteristics of unconventional Rb magneto-optical traps, Physical Review A, Vol: 98, ISSN: 1050-2947

We study several new magneto-optical trapping configurations in ⁸⁷Rb. These unconventional MOTs all use type-II transitions, where the angular momentum of the ground state is greater than or equal to that of the excited state. Some use red-detuned light, and others blue-detuned light. The properties of these MOTs are strongly influenced by the balance between opposing Doppler and Sisyphus forces, and vary widely from one configuration to another. In the blue-detuned MOT, Sisyphus cooling dominates over Doppler heating for all relevant speeds and magnetic fields. We measure the capture velocity of this MOT as a function of intensity and detuning, finding a maximum of 3.8 ± 0.1 m/s. Atomic densities are particularly high in the blue-detuned MOT, and its lifetime is limited by collisions between the trapped atoms. We present measurements of the loss rate due to these ultracold collisions as a function of laser intensity and detuning. In the red-detuned MOTs, Sisyphus heating dominates at low speeds and Doppler cooling at higher speeds. Consequently, temperatures in the red-detuned MOTs are up to a thousand times higher than in the blue-detuned MOTs. One MOT forms large ring structures, with no density at the centre, showing how atoms driven towards a non-zero equilibrium speed remain trapped by orbiting around the centre. Another MOT demonstrates that magnetic mixing of the excited-state hyperfine levels can be an important mechanism in type-II MOTs.

Journal article

Williams HJ, Caldwell L, Fitch NJ, Truppe S, Rodewald J, Hinds EA, Sauer BE, Tarbutt MRet al., 2018, Magnetic trapping and coherent control of laser-cooled molecules, Physical Review Letters, Vol: 120, ISSN: 0031-9007

We demonstrate coherent microwave control of the rotational, hyperfine and Zeeman states of ultracold CaF molecules, and the magnetic trapping of these molecules in a single, selectable quantum state. We trap about 5 X 10³ molecules for almost 2s at a temperature of 70(8) μK and a density of 1.2 X 10⁵ cm⁻³. We measure the state-specific loss rate due to collisions with background helium.

Journal article

Lim J, Almond J, Trigatzis M, Devlin J, Fitch N, Sauer B, Tarbutt M, Hinds Eet al., 2018, Laser cooled YbF molecules for measuring the electron's electric dipole moment, Physical Review Letters, Vol: 120, ISSN: 0031-9007

We demonstrate one-dimensional sub-Doppler laser cooling of a beam of YbF molecules to 100 μK. This is a key step towards a measurement of the electron's electric dipole moment using ultracold molecules. We compare the effectiveness of magnetically-assisted and polarization-gradient sub-Doppler cooling mechanisms. We model the experiment and fi nd good agreement with our data.

Journal article

Jarvis KN, Devlin JA, Wall TE, Sauer BE, Tarbutt MRet al., 2018, Blue-detuned magneto-optical trap, Physical Review Letters, Vol: 120, ISSN: 0031-9007

We present the properties and advantages of a new magneto-optical trap (MOT) where blue- detuned light drives ‘type-II’ transitions that have dark ground states. Using ⁸⁷Rb, we reach a radiation-pressure-limited density exceeding 10¹¹ cm⁻³ and a temperature below 30 μK. The phase-space density is higher than in normal atomic MOTs, and a million times higher than comparable red-detuned type-II MOTs, making the blue-detuned MOT particularly attractive for molecular MOTs which rely on type-II transitions. The loss of atoms from the trap is dominated by ultracold collisions between Rb atoms. For typical trapping conditions, we measure a loss rate of 1.8(4) × 10⁻¹⁰ cm³ s⁻¹.

Journal article

Williams H, Truppe S, Hambach M, Caldwell L, Fitch N, Hinds E, Sauer B, Tarbutt Met al., 2017, Characteristics of a magneto-optical trap of molecules, New Journal of Physics, Vol: 19, ISSN: 1367-2630

We present the properties of a magneto-optical trap (MOT) of CaFmolecules. We study the process of loading the MOT from a decelerated bu er-gas-cooled beam, and how best to slow this molecular beam in order to capture the most molecules. We determine how the number of molecules, the photon scattering rate, the oscillation frequency, damping constant, temperature, cloud size and lifetime depend on the key parameters of the MOT, especially the intensity and detuning of the main cooling laser. We compare our results to analytical and numerical models, to the properties of standard atomic MOTs, and to MOTs of SrF molecules. We load up to 2 x 10⁴ molecules, and measure a maximum scattering rate of 2.5 x 10⁶ s⁻¹ per molecule, a maximum oscillation frequency of 100 Hz, a maximum damping constant of 500 s⁻¹, and a minimum MOT rms radius of 1.5 mm. A minimum temperature of 730 μK is obtained by ramping down the laser intensity to low values. The lifetime, typically about 100 ms, is consistent with a leak out of the cooling cycle with a branching ratio of about 6 x 10⁻⁶. The MOT has a capture velocity of about 11 m/s.

Journal article

Truppe S, Hambach M, Skoff S, Bulleid N, Bumby J, Hendricks RJ, Hinds EA, Sauer BE, Tarbutt MRet al., 2017, A buffer gas beam source for short, intense and slow molecular pulses, Journal of Modern Optics, Vol: 65, Pages: 246-254, ISSN: 0950-0340

Experiments with cold molecules usually begin with a molecular source. We describe the construction and characteristics of a cryogenic buff er gas source of CaF molecules. The source emits pulses with a typical duration of 240 μs, a mean speed of about 150 m/s, and a flux of 5x 10¹⁰ molecules per steradian per pulse in a single rotational state.

Journal article

Truppe S, Williams HJ, Hambach M, Caldwell L, Fitch NJ, Hinds EA, Sauer BE, Tarbutt MRet al., 2017, Molecules cooled below the Doppler limit, Nature Physics, Vol: 13, Pages: 1173-1176, ISSN: 1745-2473

The ability to cool atoms below the Doppler limit -- the minimum temperaturereachable by Doppler cooling -- has been essential to most experiments withquantum degenerate gases, optical lattices and atomic fountains, among manyother applications. A broad set of new applications await ultracold molecules,and the extension of laser cooling to molecules has begun. A molecularmagneto-optical trap has been demonstrated, where molecules approached theDoppler limit. However, the sub-Doppler temperatures required for mostapplications have not yet been reached. Here we cool molecules to 50 uK, wellbelow the Doppler limit, using a three-dimensional optical molasses. Theseultracold molecules could be loaded into optical tweezers to trap arbitraryarrays for quantum simulation, launched into a molecular fountain for testingfundamental physics, and used to study ultracold collisions and ultracoldchemistry.

Journal article

Sauer BE, Devlin JA, Rabey IM, A big measurement of a small moment, New Journal of Physics, Vol: 19, ISSN: 1367-2630

A beam of ThO molecules has been used to make the most precise measurement of the electron's electric dipole moment (EDM) to date. In their recent paper, the ACME collaboration set out in detail their experimental and data analysis techniques. In a tour-de-force, they explain the many ways in which their apparatus can produce a signal which mimics the EDM and show how these systematic effects are measured and controlled.

Journal article

Truppe S, Williams HJ, Fitch NJ, Hambach M, Wall TE, Hinds EA, Sauer BE, Tarbutt MRet al., 2017, An intense, cold, velocity-controlled molecular beam by frequency-chirped laser slowing, NEW JOURNAL OF PHYSICS, Vol: 19, ISSN: 1367-2630

Using frequency-chirped radiation pressure slowing, we precisely control the velocity of a pulsed CaF molecular beam down to a few m s–1, compressing its velocity spread by a factor of 10 while retaining high intensity: at a velocity of 15 m s–1 the flux, measured 1.3 m from the source, is 7 × 105 molecules per cm2 per shot in a single rovibrational state. The beam is suitable for loading a magneto-optical trap or, when combined with transverse laser cooling, improving the precision of spectroscopic measurements that test fundamental physics. We compare the frequency-chirped slowing method with the more commonly used frequency-broadened slowing method.

Journal article

Rabey IM, Devlin JA, Hinds EA, Sauer BEet al., 2016, Low magnetic Johnson noise electric field plates for precision measurement, Review of Scientific Instruments, Vol: 87, ISSN: 1089-7623

We describe a parallel pair of high voltage electric field plates designed and constructed to minimise magnetic Johnson noise. They are formed by laminating glass substrates with commercially available polyimide (Kapton) tape, covered with a thin gold film. Tested in vacuum, the outgassing rate is less than 5 x 10 exp(-5) mbar.l/s. The plates have been operated at electric fields up to 8.3 kV/cm, when the leakage current is at most a few hundred pA. The design is discussed in the context of a molecular spin precession experiment to measure the permanent electric dipole moment of the electron.

Journal article

Dunseith DP, Truppe S, Hendricks RJ, Sauer BE, Hinds EA, Tarbutt MRet al., 2014, A high quality, efficiently coupled microwave cavity for trapping cold molecules, Journal of Physics B - Atomic Molecular and Optical Physics, Vol: 48, ISSN: 0953-4075

Journal article

Hendricks RJ, Holland DA, Truppe S, Sauer BE, Tarbutt MRet al., 2014, Vibrational branching ratios and hyperfine structure of 11BH and its suitability for laser cooling, Frontiers in Physics, Vol: 2, ISSN: 2296-424X

The simple structure of the BH molecule makes it an excellent candidate for direct laser cooling. We measure the branching ratios for the decay of the A1Π (v′ = 0) state to vibrational levels of the ground state, X1Σ+, and find that they are exceedingly favorable for laser cooling. We verify that the branching ratio for the spin-forbidden transition to the intermediate a3Π state is inconsequentially small. We measure the frequency of the lowest rotational transition of the X state, and the hyperfine structure in the relevant levels of both the X and A states, and determine the nuclear electric quadrupole and magnetic dipole coupling constants. Our results show that, with a relatively simple laser cooling scheme, a Zeeman slower and magneto-optical trap can be used to cool, slow and trap BH molecules.

Journal article

Zhelyazkova V, Cournol A, Wall TE, Matsushima A, Hudson JJ, Hinds EA, Tarbutt MR, Sauer BEet al., 2014, Laser cooling and slowing of CaF molecules, Physical Review A, Vol: 89, ISSN: 1094-1622

We demonstrate slowing and longitudinal cooling of a supersonic beam of CaF molecules using counterpropagating laser light resonant with a closed rotational and almost-closed vibrational transition. A group of molecules are decelerated by about 20 m/s by applying light of a fixed frequency for 1.8 ms. Their velocity spread is reduced, corresponding to a final temperature of about 300 mK. The velocity is further reduced by chirping the frequency of the light to keep it in resonance as the molecules slow down.

Journal article

Hudson JJ, Tarbutt MR, Sauer BE, Hinds EAet al., 2014, Stochastic multi-channel lock-in detection, NEW JOURNAL OF PHYSICS, Vol: 16, ISSN: 1367-2630

Journal article

Bulleid NE, Skoff SM, Hendricks RJ, Sauer BE, Hinds EA, Tarbutt MRet al., 2013, Characterization of a cryogenic beam source for atoms and molecules, Phys. Chem. Chem. Phys.

Journal article

Tarbutt MR, Sauer BE, Hudson JJ, 2013, Design for a fountain of YbF molecules to measure the electron's electric dipole moment, New Journal of Physics, Vol: 15

Journal article

Sauer BE, Devlin JA, Hudson JJ, Kara DM, Smallman IJ, Tarbutt MR, Hinds EAet al., 2013, Time reversal symmetry violation in the YbF molecule, HYPERFINE INTERACTIONS, Vol: 214, Pages: 119-126, ISSN: 0304-3843

Journal article

Kara DM, Smallman IJ, Hudson JJ, Sauer BE, Tarbutt MR, Hinds EAet al., 2012, Measurement of the electron's electric dipole moment using YbF molecules: methods and data analysis, NEW JOURNAL OF PHYSICS, Vol: 14, ISSN: 1367-2630

Journal article

Hudson JJ, Kara DM, Smallman IJ, Sauer BE, Tarbutt MR, Hinds EAet al., 2011, Improved measurement of the shape of the electron, NATURE, Vol: 473, Pages: 493-U232, ISSN: 0028-0836

Journal article

Hinds EA, Sauer BE, Hudson, Kara D, Smallman IJ, Tarbutt MRet al., Prospects for the measurement of the electron electric dipole moment using YbF, Physics Procedia, ISSN: 1875-3884

Journal article

Hinds EA, Hudson JJ, Kara D, Smallman IJ, Sauer BE, Tarbutt MRet al., Improved measurement of the shape of the electron, Nature, ISSN: 0028-0836

Journal article

Skoff SM, Hendricks RJ, Sinclair CDJ, Hudson JJ, Segal DM, Sauer BE, Hinds EA, Tarbutt MRet al., 2011, Diffusion, thermalization, and optical pumping of YbF molecules in a cold buffer-gas cell, PHYSICAL REVIEW A, Vol: 83, ISSN: 1050-2947

Journal article

Hinds EA, Skoff SM, Hendricks RJ, Sinclair CD, Hudson, Segal DM, Sauer BE, Tarbutt MRet al., Diffusion, thermalization and optical pumping of YbF molecules in a cold buffer gas cell, Physical Review A, ISSN: 1050-2947

Journal article

Wall TE, Kanem JF, Dyne JM, Hudson JJ, Sauer BE, Hinds EA, Tarbutt MRet al., 2011, Stark deceleration of CaF molecules in strong- and weak-field seeking states, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 13, Pages: 18991-18999, ISSN: 1463-9076

Journal article

Zhuang X, Le A, Steimle TC, Bulleid NE, Smallman IJ, Hendricks RJ, Skoff SM, Hudson JJ, Sauer BE, Hinds EA, Tarbutt MRet al., 2011, Franck-Condon factors and radiative lifetime of the A(2)Pi(1/2)-X-2 Sigma(+) transition of ytterbium monofluoride, YbF, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 13, Pages: 19013-19017, ISSN: 1463-9076

Journal article

Sauer BE, Hudson JJ, Kara DM, Smallman IJ, Tarbutt MR, Hinds EAet al., 2011, Prospects for the measurement of the electron electric dipole moment using YbF, 2nd International Workshop on the Physics of Fundamental Symmetries and Interactions (PSI), Publisher: ELSEVIER SCIENCE BV, ISSN: 1875-3892

Conference paper

Skoff SM, Hendricks RJ, Sinclair CDJ, Tarbutt MR, Hudson JJ, Segal DM, Sauer BE, Hinds EAet al., 2009, Doppler-free laser spectroscopy of buffer-gas-cooled molecular radicals, NEW JOURNAL OF PHYSICS, Vol: 11, ISSN: 1367-2630

Journal article

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