An Atomic Magnetometer with Spin-Projection Noise Proportional to $\sqrt{{T}_{2}}$ An Atomic Magnetometer with Spin-Projection Noise Proportional to $\sqrt{{T}_{2}}$

Haifeng Dong, Xiaofei Wang, Jimin Li +2 more

There is a common sense view for atomic magnetometers that their spin-projection-noises (SPNs) are inversely proportional to , where T 2 is the transverse relaxation time. We analyze the current atomic magnetometer types and give a counter-example of this common sense, which is the all-optical spin precession modulated three-axis atomic magnetometer proposed by our group in 2015. Unlike the other atomic magnetometers, the SPN of this kind of atomic magnetometers is proportional to due to the fact that the scale factor between P x and B can be unrelated to the transverse relaxation time T 2 . We demonstrate this irrelevance experimentally and analyze the SPN theoretically. Using short-pulse ultra-high power laser to fully polarize the atoms, the phenomenon that SPN decreases with T 2 may also be demonstrated experimentally and a new tool for researching SPN in atomic magnetometers may be realized .There is a common sense view for atomic magnetometers that their spin-projection-noises (SPNs) are inversely proportional to , where T 2 is the transverse relaxation time. We analyze the current atomic magnetometer types and give a counter-example of this common sense, which is the all-optical spin precession modulated three-axis atomic magnetometer proposed by our group in 2015. Unlike the other atomic magnetometers, the SPN of this kind of atomic magnetometers is proportional to due to the fact that the scale factor between P x and B can be unrelated to the transverse relaxation time T 2 . We demonstrate this irrelevance experimentally and analyze the SPN theoretically. Using short-pulse ultra-high power laser to fully polarize the atoms, the phenomenon that SPN decreases with T 2 may also be demonstrated experimentally and a new tool for researching SPN in atomic magnetometers may be realized .

Chinese Physics LettersJan 1, 20193 citations

Influence of noise on a magnetically sensitive atom interferometer

S. A. DeSavage, Arvind Srinivasan, Jon P. Davis +7 more

Bulletin of the American Physical SocietyMay 26, 20160 citations

Can a Quantum Nondemolition Measurement Improve the Sensitivity of an Atomic Magnetometer?

Marcis P. Auzinsh, Dmitry Budker, Derek F. Jackson Kimball +4 more

We consider the limitations due to noise (e.g., quantum projection noise and photon shot-noise) on the sensitivity of an idealized atomic magnetometer that utilizes spin squeezing induced by a continuous quantum nondemolition measurement. Such a magnetometer measures spin precession of $N$ atomic spins by detecting optical rotation of far-detuned light. We show that for very short measurement times, the optimal sensitivity scales as ${N}^{\ensuremath{-}3/4}$; if strongly squeezed probe light is used, the Heisenberg limit of ${N}^{\ensuremath{-}1}$ scaling can be achieved. However, if the measurement time exceeds ${\ensuremath{\tau}}_{\mathrm{r}\mathrm{e}\mathrm{l}}/{N}^{1/2}$ in the former case, or ${\ensuremath{\tau}}_{\mathrm{r}\mathrm{e}\mathrm{l}}/N$ in the latter, where ${\ensuremath{\tau}}_{\mathrm{r}\mathrm{e}\mathrm{l}}$ is the spin relaxation time, the scaling becomes ${N}^{\ensuremath{-}1/2}$, as for a standard shot-noise-limited magnetometer.We consider the limitations due to noise (e.g., quantum projection noise and photon shot-noise) on the sensitivity of an idealized atomic magnetometer that utilizes spin squeezing induced by a continuous quantum nondemolition measurement. Such a magnetometer measures spin precession of $N$ atomic spins by detecting optical rotation of far-detuned light. We show that for very short measurement times, the optimal sensitivity scales as ${N}^{\ensuremath{-}3/4}$; if strongly squeezed probe light is used, the Heisenberg limit of ${N}^{\ensuremath{-}1}$ scaling can be achieved. However, if the measurement time exceeds ${\ensuremath{\tau}}_{\mathrm{r}\mathrm{e}\mathrm{l}}/{N}^{1/2}$ in the former case, or ${\ensuremath{\tau}}_{\mathrm{r}\mathrm{e}\mathrm{l}}/N$ in the latter, where ${\ensuremath{\tau}}_{\mathrm{r}\mathrm{e}\mathrm{l}}$ is the spin relaxation time, the scaling becomes ${N}^{\ensuremath{-}1/2}$, as for a standard shot-noise-limited magnetometer.

arXiv:physics/0403097Physical Review LettersOct 19, 2004149 citations

Sensitivity of RF atomic magnetometer affected by the gain of balanced photodetector

Kwanruthai Sibsiri, Piyachat Wungmool, Phusit Nualpijit +4 more

Abstract An atomic magnetometer (AM) is very sensitive to magnetic fields and useful in many applications. AM works by optical interrogation of orientation of alkali-atom spins in a vapor cell. Since the sensitivity characterizes the performance of AM, it should be optimized. We investigate the effect of the gain of a balanced photodetector on the sensitivity of an RF atomic magnetometer setup. While the amplitude of RF signal (BRF) varies between 0.1-10 nT, the frequency is fixed at 100 kHz. The gain of the balanced photodetector varies between 103 - 107 V/A. the noise density and AM signal are measured to calculate the signal-to-noise ratios (SNR) and the AM sensitivity. The results show that noise density increases with the gain value. The AM signal increases with both BRF as well as the gain value. SNR increases with BRF while the AM sensitivity is independent on BRF. When the gain is increased from 103 - 105 V/A, SNR increases and reaches a maximum while the AM sensitivity decreases and reaches a minimum value of 0.4 pT/√Hz. However, SNR and the AM sensitivity are almost unchanged for the gain value of 105 - 107 V/A. Therefore, the gain of balanced photodetector in our AM setup should be set sufficiently high, at least 105 V/A.Abstract An atomic magnetometer (AM) is very sensitive to magnetic fields and useful in many applications. AM works by optical interrogation of orientation of alkali-atom spins in a vapor cell. Since the sensitivity characterizes the performance of AM, it should be optimized. We investigate the effect of the gain of a balanced photodetector on the sensitivity of an RF atomic magnetometer setup. While the amplitude of RF signal (BRF) varies between 0.1-10 nT, the frequency is fixed at 100 kHz. The gain of the balanced photodetector varies between 103 - 107 V/A. the noise density and AM signal are measured to calculate the signal-to-noise ratios (SNR) and the AM sensitivity. The results show that noise density increases with the gain value. The AM signal increases with both BRF as well as the gain value. SNR increases with BRF while the AM sensitivity is independent on BRF. When the gain is increased from 103 - 105 V/A, SNR increases and reaches a maximum while the AM sensitivity decreases and reaches a minimum value of 0.4 pT/√Hz. However, SNR and the AM sensitivity are almost unchanged for the gain value of 105 - 107 V/A. Therefore, the gain of balanced photodetector in our AM setup should be set sufficiently high, at least 105 V/A.

Journal of Physics Conference SeriesJun 1, 20250 citations

Quantum Magnetometers and Rydberg Sensors

Kai Bongs

Jan 1, 20250 citations

An Atomic Magnetometer with Spin-Projection Noise Proportional to

\sqrt{{T}_{2}}

N

atomic spins by detecting optical rotation of far-detuned light. We show that for very short measurement times, the optimal sensitivity scales as ${N}^{\ensuremath{-}3/4}$; if strongly squeezed probe light is used, the Heisenberg limit of ${N}^{\ensuremath{-}1}$ scaling can be achieved. However, if the measurement time exceeds ${\ensuremath{\tau}}_{\mathrm{r}\mathrm{e}\mathrm{l}}/{N}^{1/2}$ in the former case, or ${\ensuremath{\tau}}_{\mathrm{r}\mathrm{e}\mathrm{l}}/N$ in the latter, where ${\ensuremath{\tau}}_{\mathrm{r}\mathrm{e}\mathrm{l}}$ is the spin relaxation time, the scaling becomes ${N}^{\ensuremath{-}1/2}$, as for a standard shot-noise-limited magnetometer.