
Quantum gravimeters
Ultra-precision gravity measurement
Thanks to the advances of quantum technologies, Exail is able to provide a turn-key transportable quantum sensor measuring gravity at a level of 10-8 m/s2.
The Absolute Quantum Gravimeter (AQG) measures the acceleration of a free-falling test mass in vacuum: the ballistic free-fall of an ensemble of laser-cooled atoms is accurately monitored, and the acceleration of gravity is then inferred. This technique is one of the ballistic free-fall methods proclaimed by the BIPM (Bureau International des Poids et Mesures) as an official primary method for the measurement of gravity.
Features
Benefits
Absolute gravity measurement at a level of 10-8 m/s2 (1 μGal) in terms of sensitivity, stability and repeatability
Continuous data acquisition from a few seconds to several years
Transportable device allowing to perform surveys, time-lapse measurement of a network of reference stations or stationary measurements with the same instrument
Applications
Geophysics (reservoir monitoring and geodesy)
Civil engineering (sub-surface imaging)
Metrology
A free-fall absolute gravimeter using quantum technologies and laser-cooled atoms
The Absolute Quantum Gravimeter (AQG) is today the only commercial industry-grade gravity meter to enable continuous absolute measurements from a few seconds to several years. Being at the same time easily transportable it can be deployed anywhere on the planet both indoor and outdoor. This makes the AQG highly suitable for a wide range of applications in geophysics, metrology and civil engineering.
For high-precision gravity measurements
The AQG exploits the principle of atom interferometry with laser-cooled atoms. This unique solution is the result of more than 15 years of research conducted by our academic partners (LP2N and LNE-SYRTE). The AQG comes in 2 versions: the AQG-A for indoor use and the AQG-B for field measurements.
The AQG comes in 2 versions: the AQG-A for indoor use and the AQG-B for field measurements.

A turn-key transportable and easy-to-operate quantum sensor
Installation time: 20 minutes (no optical alignment, no mechanical assembly, no pumping required prior to measuring)
Maintenance: Low maintenance effort (no moving parts, no gasket nor belt to replace)
Robustness to ground vibration: Sub-μGal resolution even in urban environments (without any spring-based mechanical isolation device)
Autonomy: Transport and storage for several weeks without any power supply will not affect measurement capability nor require additional pumping (sealed dropping chamber)
- Software: Dedicated and user-friendly data acquisition and system controller software.
- Automated starting procedure
- Automated self-calibration procedures
- Remote monitoring and real-time data retrieval
- Data processing: Gravity data is real-time processed with corrections from local tides, atmospheric pressure, tilt variations, ocean loading and polar motion
- Auxiliary sensors: The sensor head of the AQG houses a classical 3D accelerometer, a pressure gauge, tiltmeters, temperature sensors.
Providing high-quality gravity data
Data from V. Ménoret, et al., Gravity measurements below 10−9 g with a transportable absolute quantum gravimeter, Nature Scientific Report, 8:12300 (2018)
The AQG is a flexible gravity sensor able to perform: surveys reaching a resolution of a few µGal with short integration time (Fig. 1), reference station and time-lapse measurements at 1 µGal (Fig. 2) and drift-free long-term continuous gravity monitoring with ultra-high sensitivity (Fig. 3).
These values of g are corrected from local tides, atmospheric pressure, tilt deviations and ocean loading. In Fig. 2, error bars correspond to the value of the Allan Deviation of the entire data-set calculated at one hour integration time, which corresponds to the statistical uncertainty of this measurement.
This uninterrupted time series has lasted one month and shows local tides. When data are averaged over long durations, the AQG provides drift-free sub-μGal stability.
Simple and compact quantum gravimeter
The design of the AQG relies on a patented opto-mechanical architecture using a pyramidal retro-reflector. This configuration allows to perform the measurement sequence with a single laser beam instead of up to eight usually, leading to a drastic simplification of the instrument.
High-reliability fibered optical components
The laser system developed by Exail relies on the use of lasers operating at 1560 nm. This approach therefore gives access to a wide variety of high performance fibered optical components, originally developed for high-bit-rate optical communication systems. Thanks to the technological efforts conducted over the last 20 years by the telecom industry, these components present unique features:
- Fibered components: no optical alignment required
- Remarkable optical and electrical performances
- Compliance with Telcordia qualification procedures (extended temperature range)
- High reliability (lifetime > 50 000 h).
High immunity to ground vibrations
The AQG efficiently rejects ground vibration noise with an active compensation technique that does not require any mechanical isolation device or superspring.
Specifications of the AQG-A and AQG-B
Performance
![]() AQG-A (indoor) | ![]() AQG-B (field) | |
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Typical Precision at quiet site | 500 nm/s²/sqrt(t) 1 | 500 nm/s²/sqrt(t)1, 2 |
Long-term stability | ≤ 20 nm/s² | ≤ 20 nm/s² |
Trueness | ≤ 150 nm/s² 3 | ≤ 150 nm/s² 3 |
Repeatability | ≤ 50 nm/s² | ≤ 50 nm/s² |
Cycling frequency | >1 Hz | >1 Hz |
Physics package
Number of boxes / Maximum mass | 3 / 45 Kg / < 100 Kg | 5 / 40 kg /< 140 kg |
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Dimensions of sensor head | 1 module: Ø= 40 cm / H= 100 cm / (tripod incl.) | 1 module: Ø= 40 cm / H=100 cm / (tripod incl.) |
Dimensions of control unit | 1 module: H = 70 cm x W = 55 cm x L = 70 cm | 2 modules: h = 41 cm x w = 59 cm x l = 105 cm |
Length of the cable between | 15 m | 15 m |
Warm up time (typical) / | 2 h | 2 h |
System Interface & Control
Control system | External computer (Linux OS) | External computer (Linux OS) |
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User Interface | Dedicated software and set-up tool | Dedicated software and set-up tool |
Remote Control and Monitoring | With TeamViewer | With TeamViewer |
Data format | .csv (All corrections (tides, ocean loading, atmospheric pressure) are recorded for easy post-processing | .csv (All corrections (tides, ocean loading, atmospheric pressure) are recorded for easy post-processing |
Environmental & Physical Specifications
Operating Temperature / Storage temperature | [18-24] °C / [5-30] °C | [0 ; 40] °C / [5 ; 30] °C |
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Humidity | 60% | 60% |
AC DC Power requirements
Operating Voltage | 110 V/230 V | 110 V/230 V |
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Voltage level | 350 W | 12V or 24 V |
Operating power consumption | 500 W | |