The inclusion of this clock is significant, as it is a sophisticated technology possessed by only a select few countries, highlighting India’s technical capabilities in this field. What makes our Rubidium Atomic Clock even more special, is that it was indigenously developed and was created by the Space Applications Centre in Ahmedabad. And yet, India’s ISRO is only the fifth space agency ever to employ it. Although it is a clock and will be used to keep track of time, the sophistication and accuracy with which it works have made it indispensable for most space missions. The atomic clock that has been used in the NVS-1 NavIC satellite is a highly technical piece of engineering. So rare and difficult is this clock to make, that only 5 countries so far have used it for their space missions. While technologically, every component on board the NVS-1 NavIC satellite is an engineering marvel in and of itself, one component that really stands out is the Rubidium Atomic Clock that has been placed on board the satellite. Other highly charged ions are particularly sensitive to changes in the fine structure constant and to certain dark matter candidates that are required in models beyond the Standard Model but could not be detected with previous methods.India made a significant jump towards self-dependency after the successful launch and deployment of its NVS-1 NavIC satellite. These include atomic systems that can be used to search for extensions of the Standard Model of particle physics. The methods used are universally applicable and allow many different highly charged ions to be studied. The researchers have thus created a serious competitor to existing optical atomic clocks based on, for example, individual ytterbium ions or neutral strontium atoms. 'We expect a further reduction of the uncertainty through technical improvements, which should bring us into the range of the best atomic clocks,' says research group leader Piet Schmidt. They achieved a measurement uncertainty of 2 parts in 10 17 - comparable to many currently operated optical atomic clocks. To do this, they had to analyse the system in great detail in order to understand, for example, the movement of the highly charged ion and the effects of external interference fields. Now the researchers have successfully taken the next step: They have realised an optical atomic clock based on thirteen-fold charged argon ions and compared the ticking with the existing ytterbium ion clock at PTB. These results were already published in Nature in 2020 and in Physical Review X in 2021.

This corresponded to a temperature of 200 millionths of a kelvin above absolute zero. Subsequently, a quantum algorithm developed at PTB succeeded in cooling the highly charged ion even further, namely close to the quantum mechanical ground state. An advanced cryogenic trap system was then built at MPIK and finalized at PTB for the following experiments, which were carried out in part by students switching between the institutions. This allows the highly charged ion to be cooled indirectly and studied by means of the beryllium ion. This was solved by a collaboration between MPIK in Heidelberg and the QUEST Institute at PTB by isolating a single highly charged argon ion from a hot plasma and storing it in an ion trap together with a singly charged beryllium ion. Because of their extreme atomic structure, highly charged ions can't be cooled directly with laser light, and standard detection methods can't be used either.

Highly charged ions, however, are produced by creating an extremely hot plasma. This hope has already been fulfilled: 'We were able to detect the quantum electrodynamic nuclear recoil, an important theoretical prediction, in a five-electron system, which has not been achieved in any other experiment before.'īeforehand, the team had to solve some fundamental problems, such as detection and cooling, in years of work: For atomic clocks, one has to cool the particles down extremely in order to stop them as much as possible and thus read out their frequency at rest. 'Therefore, we expected that an optical atomic clock with highly charged ions would help us to better test these fundamental theories,' explains PTB physicist Lukas Spieß. For this reason, highly charged ions react less strongly to interference from external electromagnetic fields, but become more sensitive probes of fundamental effects of special relativity, quantum electrodynamics and the atomic nucleus.

This is why the outermost electrons are more strongly bound to the atomic nucleus than in neutral or weakly charged atoms. They are so called because they have lost many electrons and therefore have a high positive charge. Highly charged ions are a common form of matter in the cosmos, where they are found, for example, in the sun or other stars.

Atomic clocks with accuracy