Quantum Engineered States for Optical Clocks and Atomic Sensors
Clocks with the highest precision are key to major applications such as the realization and dissemination of the unit of time of the international system of units, the realization of the international atomic time, global navigation satellite systems (GPS, GALILEO, etc.) and the exploration of fundamental physical laws. Further, new applications are anticipated, directly enabled by the gain in precision possible with the new generation of optical clocks. One of the key factors for gaining in precision is the capability of the clock to measure quickly with excellent uncertainty, i.e. the clock stability. Fundamental limits to the stability of optical clocks are extremely low. JRP EXL01 aims at exploring ways reach these limits beyond the current limitations. For this purpose, JRP EXL01 will investigate how to use possibilities offered by quantum mechanics to generate, detect and use specially designed states of an ensemble of several particles, here atoms or ions used for the clock. These states and associated methods to detect them have the potential to enhance the stability of optical clocks. JRP EXL01 aims at identifying the most promising approaches, taking into account the specific requirements of precision measurements.
Need for the project
The best atomic clocks today have accuracy around 1 part in 1017. Accuracies of 10-18 are possible in the near future. However, investigating the physical phenomena, understanding the associated shifts of the clock frequency and using clocks at the 10-18 level is currently hindered by the prohibitively long time needed to measure at this level. In current state-of-the-art systems, the stability is limited by two main causes, depending on the type of system. One limitation arises from the limited number of particles used for the clock, via the standard quantum projection noise, which is inversely proportional to the square root of the number of particles. The second limitation (called Dick effect) is due to the large amount of dead time of the sequence used to probe the clock transition combined with the probe laser frequency noise. This dead time is associated to the need to gather, to cool and to prepare atoms or ions before the probe period and to the detection of the atomic systems after probe period. The proposed JRP addresses techniques with the potential to overcome these limitations by the introduction of quantum-mechanical entanglement to the field of optical clocks. Limitations faced by optical clocks are reminiscent of limitations in other atom-based sensors, such as accelerometers, gravimeters, gyrometers or magnetometers. The research undertaken within JRP EXL01 will benefit all these sensors. JRP EXL01 is designed to account for the need of these sensors and more generally, to maximize exchanges and cross-fertilization between optical clocks and several other fields: atom interferometry, quantum gases, quantum information processing.
Scientific and technical objectives
The goal of the JRP EXL01 is to identify, to develop and to implement methods that can improve the stability of optical clocks and of atom-based sensors, while taking into account the specific requirements of precision measurements. These researches will build on several state-of-the-art optical clocks present in European national metrology institutes which are JRP-partners. JRP EXL01 is intrinsically oriented toward the exploration of new and innovative approaches. JRP EXL01 is designed to have maximized input from the academic sector, via three Research Excellence Grants integrated to the project. Within JRP EXL01, we will investigate several approaches to generate quantum engineered states suitable for clocks and atom-based sensors, i.e. states of several particles showing quantum entanglement that can be beneficial to the clock. We will develop technologies necessary to manipulate and benefit from these states, like for instance, low noise detection, quantum non-destructive detection or micro-fabricated ion traps. Next, we will design optimized ways to use these states in our clocks or atom-based sensors. Finally, we will perform proof-of- principle experiments demonstrating the benefit of quantum engineered states to atomic spectroscopy and to the clock operation. Proof-of-principle experiments will compare spectroscopy and clock stability with and without our methods on the same system, everything else being equal. They will show spectroscopy and clock stability beyond the limit due to the Dick effect and to the quantum projection noise. Comparing the two situations (with or without quantum engineered states/methods on the same system) will quantify the benefit
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