A self-sustaining atomic magnetometer with τ−1 averaging property

Abstract

Quantum measurement using coherent superposition of intrinsic atomic states has the advantage of being absolute measurement and can form metrological standards. One example is the absolute measurement of magnetic field by monitoring the Larmor precession of atomic spins whilst another being the Ramsey type atomic clock. Yet, in almost all coherent quantum measurement, the precision is limited by the coherence time beyond which, the uncertainty decreases only as τ−1/2. Here we show that by non-destructively measuring the phase of the Larmor precession and regenerating the coherence via optical pumping, the self-sustaining Larmor precession signal can persist indefinitely. Consequently, the precision of the magnetometer increases with time following a much faster τ−1 rule. A mean sensitivity of 240 from 1 Hz to 10 Hz is realized, being close to the shot noise level. This method of coherence regeneration may also find important applications in improving the performance of atomic clocks.

Floquet space exploration for the dual-dressing of a qubit

“…This spin probe is analogue to the self-sustaining Larmor precession signal detected in the magnetometer experiments of Refs. 54 , 55 .…”

Indirect pumping bell–bloom magnetometer

“…This bandwidth could be greatly increased by self-oscillation method. [6] And the sensitivity near the bandwidth frequency is found to be 100 fT/Hz 1/2 . Frequency/Hz Fig.…”

“…[1] Compared to the double resonance magnetometer, BBM has its advantage of being all optical, which does not produce any radio frequency fields, and has become an important type of atomic magnetometer. [2][3][4][5][6][7] The precession of the atomic spin polarization can be monitored by the paramagnetic Faraday rotation of another linearly polarized probe beam. [8] Such geometry is back-action evading and has the potential of achieving sensitivities beyond the standard quantum limit.…”

Combined effect of light intensity and temperature on the magnetic resonance linewidth in alkali vapor cell with buffer gas

“…[2] In the 1950s, Kaslter et al developed optical methods to polarize and probe the spin of unpaired electron. [3,4] Since then, there appears a lot of researches on different magnetic resonance magnetometers, such as Bell-Bloom magnetometer, [5][6][7] Mx magnetomter, [8][9][10] Mz magnetomter, [11,12] CPT (coherent population trapping) magnetometer, [13,14] and SERF (spin exchange relaxation free) magnetometer, [15][16][17][18] etc. One of the most important issues of these magnetometers is the magnetic resonance linewidth which is related directly to the fundamental sensitivity of atomic magnetometer by δ B = (1/γ) ∆ω/nV t, where ∆ω is the linewidth of the magnetometer, n is the density of the alkali atoms, V is the cell volume, t is the measurement time, and γ is the gyromagnetic ratio of the alkali atom.…”

“…When the alkali atoms encounter the bare glass surface of the cell wall, it can be captured for a little while (10 −5 s-10 −7 s) and be completely depolarized by the ions and molecules within the glass. [24] Paraffin, [25] OTS (octadecyltrichlorosilane), [26][27][28] and alkene [7,29] are all proved to be able to reduce the relaxation rate due to cell wall.…”