A new limit on the electric dipole moment of the electron
1 December 2018
The Standard Model of elementary particle physics predicts asymmetry of the electron charge distribution along the spin direction, i.e., an electric dipole moment (EDM) whose value is much smaller than can be measured in today’s experiments. Some theories introducing a “new physics” beyond the Standard Model give a much larger EDM, and these predictions can already be verified. In the ACME II experiment, a new limit on electron EDM |de|<1,1 × 10-29 e cm was established which is an order of magnitude better than the limit obtained five years ago by the ACME collaboration in a similar experiment with thorium single-oxide molecules. The strong intramolecular electric field in ThO molecules interacts with the electrons EDM and induces precession of their spins. The EDM value can be found from the difference of precession angles in quantum states with different EDM directions. The measurements were performed through molecules exposure to laser light and detection of their fluorescent radiation. The experimental data also suggest new limits on admissible “new physics” parameters. In particular, for some versions of the supersymmetry theory some difficulties arise, which lowers the chance to discover supersymmetric particles at the Large Hadron Collider.
Source: Nature 562 355 (2018)
Count of the number of phonons in a microoscillator
1 December 2018
Vibrations of mechanical oscillators near a quantum level (with small occupation numbers of phonons) have already been observed in some experiments. To measure the states and to manipulate vibrations, the oscillators were coupled with superconducting qubits, but strong coupling has not been reached earlier. The researchers from the National Institute of Standards and Technology and the University of Colorado, Boulder (USA) J.J. Viennot, X. Ma, and K.W. Lehnert used for this purpose a charge-sensitive qubit and an oscillator made of an aluminum membrane several µm in size. Positive and negative charges cumulated at different ends of the membrane under an electric field. Mechanical 25 MHz vibrations set the charges in motion and they affected the qubit leading to a shift of its fundamental frequency of 4 GHz by 0.52 MHz (in terms of one phonon). The information on phonon distribution was contained in the measured spectral function of the qubit. Investigated was also the effect on the system of the microwave pulses on the lower sideband of qubit vibrations modulated by the oscillator frequency. This signal made it possible to control the oscillator Fock states up to approximately seven phonons. It was used to cool the oscillator, thus raising its ground state population by a factor of eight. This approach can find application in quantum micromechanics.
Source: Phys. Rev. Lett. 121 183601 (2018)
A dielectric resonant antenna
1 December 2018
P. Kapitanova (St. Petersburg National Research University of Information Technologies, Mechanics and Optics) with co-authors designed a dielectric resonant antenna intended for a coherent manipulation over a large ensemble of NV enters in a diamond. The antenna has the form of a hollow dielectric cylinder 12.5 mm in diameter and 6 mm in height. A diamond with NV centers was placed inside the cylinder on its axis. A resonance electromagnetic mode with frequency of 2.84 GHz is excited by a conducting loop at the antenna’s pedestal, the magnetic field inside the cylinder being homogeneous to a high degree of accuracy. Owing to this fact, the electron spins of NV centers are well synchronized, which strengthens the output optical signal. The Rabi frequency of 10 MHz was reached and was constant along the sample to an accuracy of 1 %. Such an antenna can be used in ultrasensitive sensors.
Source: Ïèñüìà â ÆÝÒÔ 108 625 (2018)
1 December 2018
The operation of optical gyroscopes is based on measurement of the phase difference of light beams that passed along a ring waveguidein two directions (for the Sagnac effect see Phys. Usp. 45 793 (2002) and Phys. Usp. 57 714 (2014)). Optical gyroscopes have no mobile mechanical parts, but their sensitivity is limited by thermal fluctuations and fabrication mismatch. P.P. Khial, A.D. White and A. Hajimiri (California Institute of Technology, USA) demonstrated a new construction of the optical gyroscope with sensitivity higher by 1-2 orders of magnitude than that of optical fiber gyroscopes and has only 2 mm2 in area. In the new device, being driven by an electronic switch the optical inlets and outlets change places, and a pair of rings is used. Slow thermal fluctuations affect similarly the light propagating in both directions, and therefore the switch of directions counterbalances the influence of fluctuations. Being small, the new gyroscope can be integrated in different mobile devices.
Source: Nature Photonics 12 671 (2018)
An assembling galactic cluster in the Early Universe
1 December 2018
The observed galactic clusters occurred rather recently at red shifts z<1-2.5. In earlier epochs, galactic clusters were very rare, but there existed their predecessors, namely, nonvirialized regions (those that have not reached gravitational equilibrium) with a heightened concentration of galaxies, i.e., protoclusters. The properties of protoclusters are of interest, in particular, for inhomogeneous reionization models. L. Jiang (Peking University, China) with co-authors implemented the search for protoclusters at z>5. Chosen were candidates from the review of galaxies Subaru/XMM-Newton, which were then examined by a spectrograph on 6.5-m Magellan telescopes in Chili. This method was used to investigate the region on the celestial sphere 4 square degrees in size, and a giant protocluster of galaxies at z=5.7 was revealed. It has a mass of 3.6 × 1015M☉ and occupies a volume of 35×35×35 comoving Mpc2.
Source: Nature Astronomy 2 962 (2018)
The Extracts from the Internet is a section of Uspekhi Fizicheskih Nauk (Physics Uspekhi) the monthly rewiew journal of the current state of the most topical problems in physics and in associated fields. The presented News is devoted to the fundamental discoveries of physics and astrophysics.
Permanent editor is Yu.N. Eroshenko.
It is compiled from a multitude of Internet sources.