Akio Kawasaki

All Publications

• Entanglement on an optical atomic-clock transition. Nature Pedrozo-Penafiel, E., Colombo, S., Shu, C., Adiyatullin, A. F., Li, Z., Mendez, E., Braverman, B., Kawasaki, A., Akamatsu, D., Xiao, Y., Vuletic, V. 2020; 588 (7838): 414–18

  Abstract

  State-of-the-art atomic clocks are based on the precise detection of the energy difference between two atomic levels, which is measured in terms of the quantum phase accumulated over a given time interval1-4. The stability of optical-lattice clocks (OLCs) is limited both by the interrupted interrogation of the atomic system by the local-oscillator laser (Dick noise5) and by the standard quantum limit (SQL) that arises from the quantum noise associated with discrete measurement outcomes. Although schemes for removing the Dick noise have been recently proposed and implemented4,6-8, performance beyond the SQL by engineering quantum correlations (entanglement) between atoms9-20 has been demonstrated only in proof-of-principle experiments with microwave clocks of limited stability. The generation of entanglement on an optical-clock transition and operation of an OLC beyond the SQL represent important goals in quantum metrology, but have not yet been demonstrated experimentally16. Here we report the creation of a many-atom entangled state on an OLC transition, and use it to demonstrate a Ramsey sequence with an Allan deviation below the SQL after subtraction of the local-oscillator noise. We achieve a metrological gain of [Formula: see text] decibels over the SQL by using an ensemble consisting of a few hundred ytterbium-171 atoms, corresponding to a reduction of the averaging time by a factor of 2.8±0.3. Our results are currently limited by the phase noise of the local oscillator and Dick noise, but demonstrate the possible performance improvement in state-of-the-art OLCs1-4 through the use of entanglement. This will enable further advances in timekeeping precision and accuracy, with many scientific and technological applications, including precision tests of the fundamental laws of physics21-23, geodesy24-26 and gravitational-wave detection27.

  View details for DOI 10.1038/s41586-020-3006-1

  View details for PubMedID 33328668

• Evidence for Nonlinear Isotope Shift in Yb+ Search for New Boson PHYSICAL REVIEW LETTERS Counts, I., Hur, J., Craik, D., Jeon, H., Leung, C., Berengut, J. C., Geddes, A., Kawasaki, A., Jhe, W., Vuletic, V. 2020; 125 (12)

  View details for DOI 10.1103/PhysRevLett.125.123002

  View details for Web of Science ID 000569266900005

• High sensitivity, levitated microsphere apparatus for short-distance force measurements. The Review of scientific instruments Kawasaki, A., Fieguth, A., Priel, N., Blakemore, C. P., Martin, D., Gratta, G. 2020; 91 (8): 083201

  Abstract

  A high sensitivity force sensor based on dielectric microspheres in vacuum, optically trapped by a single, upward-propagating laser beam, is described. Off-axis parabolic mirrors are used both to focus the 1064 nm trapping beam and to recollimate it to provide information on the horizontal position of the microsphere. The vertical degree of freedom is readout by forming an interferometer between the light retroreflected by the microsphere and a reference beam, hence eliminating the need for auxiliary beams. The focus of the trapping beam has a 1/E2 radius of 3.2 m and small non-Gaussian tails, suitable for bringing devices close to the trapped microsphere without disturbing the optical field. Electrodes surrounding the trapping region provide excellent control of the electric field, which can be used to drive the translational degrees of freedom of a charged microsphere and the rotational degrees of freedom of a neutral microsphere, coupling to its electric dipole moment. With this control, the charge state can be determined with single electron precision, the mass of individual microspheres can be measured, and empirical calibrations of the force sensitivity can be made for each microsphere. A force noise of <1 * 10-17 N/Hz, which is comparable to previous reports, is measured on all three degrees of freedom for 4.7 m diameter, 84 pg silica microspheres. Various devices have been brought within 1.6 m of the surface of a trapped microsphere. Metrology in the trapping region is provided by two custom-designed microscopes providing views in the horizontal and one of the vertical planes. The apparatus opens the way to performing high sensitivity three-dimensional force measurements at a short distance.

  View details for DOI 10.1063/5.0011759

  View details for PubMedID 32872897

• Trapping Yb-171 atoms into a one-dimensional optical lattice with a small waist PHYSICAL REVIEW A Kawasaki, A., Braverman, B., Pedrozo-Penafiel, E., Shu, C., Colombo, S., Li, Z., Vuletic, V. 2020; 102 (1)

  View details for DOI 10.1103/PhysRevA.102.013114

  View details for Web of Science ID 000554458800001

• Measurement of the Newtonian constant of gravitation G by precision displacement sensors CLASSICAL AND QUANTUM GRAVITY Kawasaki, A. 2020; 37 (7)

  View details for DOI 10.1088/1361-6382/ab6f80

  View details for Web of Science ID 000537357400002

• Absolute pressure and gas species identification with an optically levitated rotor JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Blakemore, C. P., Martin, D., Fieguth, A., Kawasaki, A., Priel, N., Rider, A. D., Gratta, G. 2020; 38 (2)

  View details for DOI 10.1116/1.5139638

  View details for Web of Science ID 000569100800022

• Evidence for Nonlinear Isotope Shift in Yb^{+} Search for New Boson. Physical review letters Counts, I., Hur, J., Aude Craik, D. P., Jeon, H., Leung, C., Berengut, J. C., Geddes, A., Kawasaki, A., Jhe, W., Vuletić, V. 2020; 125 (12): 123002

  Abstract

  We measure isotope shifts for five Yb^{+} isotopes with zero nuclear spin on two narrow optical quadrupole transitions ^{2}S_{1/2}→^{2}D_{3/2}, ^{2}S_{1/2}→^{2}D_{5/2} with an accuracy of ∼300  Hz. The corresponding King plot shows a 3×10^{-7} deviation from linearity at the 3σ uncertainty level. Such a nonlinearity can indicate physics beyond the Standard Model (SM) in the form of a new bosonic force carrier, or arise from higher-order nuclear effects within the SM. We identify the quadratic field shift as a possible nuclear contributor to the nonlinearity at the observed scale, and show how the nonlinearity pattern can be used in future, more accurate measurements to separate a new-boson signal from nuclear effects.

  View details for DOI 10.1103/PhysRevLett.125.123002

  View details for PubMedID 33016768

• Robust kHz-linewidth distributed Bragg reflector laser with optoelectronic feedback OPTICS EXPRESS Yamoah, M., Braverman, B., Pedrozo-Penafiel, E., Kawasaki, A., Zlatkovic, B., Vuletic, V. 2019; 27 (26): 37714–20

  Abstract

  We demonstrate a combination of optical and electronic feedback that significantly narrows the linewidth of distributed Bragg reflector lasers (DBRs). We use optical feedback from a long external fiber path to reduce the high-frequency noise of the laser. An electro-optic modulator placed inside the optical feedback path allows us to apply electronic feedback to the laser frequency with very large bandwidth, enabling robust and stable locking to a reference cavity that suppresses low-frequency components of laser noise. The combination of optical and electronic feedback allows us to significantly lower the frequency noise power spectral density of the laser across all frequencies and narrow its linewidth from a free-running value of 1.1 MHz to a stabilized value of 1.9 kHz, limited by the detection system resolution. This approach enables the construction of robust lasers with sub-kHz linewidth based on DBRs across a broad range of wavelengths.

  View details for DOI 10.1364/OE.27.037714

  View details for Web of Science ID 000507254300053

  View details for PubMedID 31878548

• Precision Mass and Density Measurement of Individual Optically Levitated Microspheres PHYSICAL REVIEW APPLIED Blakemore, C. P., Rider, A. D., Roy, S., Fieguth, A., Kawasaki, A., Priel, N., Gratta, G. 2019; 12 (2)

  View details for DOI 10.1103/PhysRevApplied.12.024037

  View details for Web of Science ID 000481614300003

• Near-Unitary Spin Squeezing in Yb-171 PHYSICAL REVIEW LETTERS Braverman, B., Kawasaki, A., Pedrozo-Penafiel, E., Colombo, S., Shu, C., Li, Z., Mendez, E., Yamoah, M., Salvi, L., Akamatsu, D., Xiao, Y., Vuletic, V. 2019; 122 (22)

  View details for DOI 10.1103/PhysRevLett.122.223203

  View details for Web of Science ID 000470882900002

• Electrically driven, optically levitated microscopic rotors PHYSICAL REVIEW A Rider, A. D., Blakemore, C. P., Kawasaki, A., Priel, N., Roy, S., Gratta, G. 2019; 99 (4)

  View details for DOI 10.1103/PhysRevA.99.041802

  View details for Web of Science ID 000466234500001

• Three-dimensional force-field microscopy with optically levitated microspheres PHYSICAL REVIEW A Blakemore, C. P., Rider, A. D., Roy, S., Wang, Q., Kawasaki, A., Gratta, G. 2019; 99 (2)

  View details for DOI 10.1103/PhysRevA.99.023816

  View details for Web of Science ID 000458132800010

• Geometrically asymmetric optical cavity for strong atom-photon coupling PHYSICAL REVIEW A Kawasaki, A., Braverman, B., Pedrozo-Penafiel, E., Shu, C., Colombo, S., Li, Z., Ozel, O., Chen, W., Salvi, L., Heinz, A., Levonian, D., Akamatsu, D., Xiao, Y., Vuletic, V. 2019; 99 (1)

  View details for DOI 10.1103/PhysRevA.99.013437

  View details for Web of Science ID 000457690800001

• Search for kilogram-scale dark matter with precision displacement sensors PHYSICAL REVIEW D Kawasaki, A. 2019; 99 (2)

  View details for DOI 10.1103/PhysRevD.99.023005

  View details for Web of Science ID 000455062100001

• Impact of non-unitary spin squeezing on atomic clock performance NEW JOURNAL OF PHYSICS Braverman, B., Kawasaki, A., Vuletic, V. 2018; 20

  View details for DOI 10.1088/1367-2630/aae563

  View details for Web of Science ID 000447167400003