Atomic interferometer

An atomic interferometer is an interferometer that uses the wave properties of atoms . With atomic interferometers, fundamental constants such as the gravitational constant can be determined with high accuracy, but possibly also phenomena such as gravitational waves can be investigated.

overview

Interferometry is based on wave properties. As was postulated by Louis de Broglie in his dissertation, particles, including atoms , can behave like waves (so-called wave-particle dualism ) - this is a central principle of quantum mechanics . If very high accuracy is required in experiments, atomic interferometers are increasingly being used, since atoms have a very small De Broglie wavelength . Some experiments now even use molecules to reach even smaller wavelengths and to search for the limits of the validity of quantum mechanics. In many experiments with atoms, the roles of matter and light are reversed compared to laser- based interferometers; Instead of light, matter interferes. The quantum states of the interfering atoms are controlled by laser radiation. The effect of these laser beams corresponds to z. B. the mirrors and beam splitters in an optical interferometer.

Interferometer types

The use of atoms makes it possible to use higher frequencies (and thus accuracies) than with light , but at the same time atoms are also more exposed to gravity . In some devices, the atoms are ejected upward and interferometry occurs while the atoms are in flight or in free fall. In other experiments, additional forces are applied to compensate for the gravitational forces. In principle, these guided systems allow unlimited measurement times, but their coherence is still being discussed. Recent theoretical investigations suggest that coherence is maintained in guided systems, but this has yet to be confirmed experimentally.

The first atomic interferometers used slits or wires as beam splitters and mirrors. Later systems, especially the guided, used light forces for the division and reflection of the matter wave.

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Examples

group	year	Atomic types	method	Measured effect (s)
Pritchard	1991	Well , well 2	nanostructured diffraction grating	Polarizability , refractive index
Clauser	1994	K	Talbot-Lau interferometer (uses the Talbot effect )
Zeilinger	1995	Ar	Diffraction grating from standing light waves
Sterr (PTB)			Ramsey Bordé	Polarizability, Aharonov-Bohm effect : exp / theo , Sagnac ${\displaystyle 0{,}99\pm 0{,}022}$ ${\displaystyle 0{,}3\ \mathrm {rad/s{\sqrt {Hz}}} }$
Kasevich , Chu			Doppler effect on falling atoms	Gravimeter : Rotation: , fine structure constant : ${\displaystyle 3\cdot 10^{-10}}$ ${\displaystyle 2\cdot 10^{-8}\ \mathrm {/s/{\sqrt {Hz}}} }$ ${\displaystyle \alpha \pm 1{,}5\cdot 10^{-9}}$

history

The separation of matter waves of complete atoms was first observed by Estermann and Stern in 1929 when hydrogen and helium rays were diffracted on a surface by sodium chloride . The first reported modern atomic interferometers in 1991 were a double slit experiment according to Young with metastable helium atoms and a microstructured double slit by Carnal and Mlynek and an interferometer with three microstructured diffraction gratings and sodium atoms in the Pritchard group at MIT. Shortly thereafter, the Physikalisch-Technische Bundesanstalt (PTB) found that an optical Ramsey spectrometer, which is usually used in atomic clocks, can also be used as an atomic interferometer. The greatest spatial separation between packets of partial waves was achieved by means of laser cooling and stimulated Raman transitions by Chu and co-workers at Stanford.

literature

• Alexander D. Cronin, Jörg Schmiedmayer, David E. Pritchard: Optics and interferometry with atoms and molecules . In: Reviews of Modern Physics . tape 81 , no. 3 , July 28, 2009, p. 1051-1129 , doi : 10.1103 / RevModPhys.81.1051 .

• CS Adams: Atom Optics . In: Contemporary Physics . tape 35 , no. 1 , 1994, p. 1–19 , doi : 10.1080 / 00107519408217492 (overview of atom-light interactions).

• Paul R. Berman (Ed.): Atom Interferometry . Academic Press, 1997, ISBN 978-0-08-052768-0 (Detailed overview of atomic interferometers at the time; good introductions and theory).

• Uwe Sterr, Fritz Riehle: Atomic interferometry . In: PTB-Mitteilungen . tape 119 , no. 2 , 2009, p. 159–166 ( atomic interferometry ( memento of December 29, 2013 in the Internet Archive ) [PDF; 5,6 MB ; accessed on June 17, 2016]).

Individual evidence

1. ↑ Savas Dimopoulos, Peter W. Graham, Jason M. Hogan, Mark A. Kasevich, Surjeet Rajendran: Gravitational wave detection with atom interferometry . In: Physics Letters B . tape 678 , no. 1 , July 6, 2009, p. 37-40 , doi : 10.1016 / j.physletb.2009.06.011 .
2. ↑ Klaus Hornberger, Stefan Gerlich, Philipp Haslinger, Stefan Nimmrichter, Markus Arndt: Colloquium: Quantum interference of clusters and molecules . In: Reviews of Modern Physics . tape 84 , no. 1 , February 8, 2012, p. 157-173 , doi : 10.1103 / RevModPhys.84.157 .
3. ^ Ernst M. Rasel, Markus K. Oberthaler, Herman Batelaan, Jörg Schmiedmayer, Anton Zeilinger: Atom Wave Interferometry with Diffraction Gratings of Light . In: Physical Review Letters . tape 75 , no. 14 , October 2, 1995, p. 2633-2637 , doi : 10.1103 / PhysRevLett.75.2633 .
4. ^ I. Estermann, O. Stern: Diffraction of molecular beams . In: Journal of Physics . tape 61 , no. 1-2 , January 1, 1930, pp. 95-125 , doi : 10.1007 / BF01340293 .
5. ^ O. Carnal, J. Mlynek: Young's double-slit experiment with atoms: A simple atom interferometer . In: Physical Review Letters . tape 66 , no. 21 , May 27, 1991, pp. 2689-2692 , doi : 10.1103 / PhysRevLett.66.2689 .
6. ↑ David W. Keith, Christopher R. Ekstrom, Quentin A. Turchette, David E. Pritchard: An interferometer for atoms . In: Physical Review Letters . tape 66 , no. 21 , May 27, 1991, pp. 2693-2696 , doi : 10.1103 / PhysRevLett.66.2693 .
7. ^ F. Riehle, Th. Kisters, A. Witte, J. Helmcke, Ch. J. Bordé: Optical Ramsey spectroscopy in a rotating frame: Sagnac effect in a matter-wave interferometer . In: Physical Review Letters . tape 67 , no. 2 , July 8, 1991, p. 177-180 , doi : 10.1103 / PhysRevLett.67.177 .
8. ↑ M. Kasevich, S. Chu: Measurement of the gravitational acceleration of an atom with a light-pulse atom interferometer . In: Applied Physics B . tape 54 , no. 5 , May 1, 1992, pp. 321-332 , doi : 10.1007 / BF00325375 .