Improvement of an Atomic Clock using Squeezed Vacuum

Abstract

Since the pioneering work of Ramsey, atom interferometers are employed for precision metrology, in particular to measure time and to realize the second. In a classical interferometer, an ensemble of atoms is prepared in one of the two input states, whereas the second one is left empty. In this case, the vacuum noise restricts the precision of the interferometer to the standard quantum limit (SQL). Here, we propose and experimentally demonstrate a novel clock configuration that surpasses the SQL by squeezing the vacuum in the empty input state. We create a squeezed vacuum state containing an average of 0.75 atoms to improve the clock sensitivity of 10000 atoms by 2.05_{-0.37}^{+0.34} dB. The SQL poses a significant limitation for today's microwave fountain clocks, which serve as the main time reference. We evaluate the major technical limitations and challenges for devising a next generation of fountain clocks based on atomic squeezed vacuum.

Optimal quantum interferometry robust to detection noise using spin-1 atomic condensates

“…will lead to lower values of the QFI than ones obtained from the three optimal interferometers established by us. Alternatively, the very initial time evolution can be treated under the undepleted pump approximation [6,7,33,39] in which the macroscopically populated mode m F =0 acts as a source and injects atoms to the side modes. However, the approximation overestimates the values of the QFI in later times as discussed and demonstrated in appendix F. The best interferometric configurations identified in this section are summarized in figure 3.…”

“…It turns out that the one among realatively easy to measure experimentally observables, namely J Y Q , ,  =ˆ, i.e. 6 The general definition of the classical Fisher Information [47] is given by p x p x…”

“…We consider the non-classical states of the system generated from the initial polar state in the absence of an external magnetic field. The specific configuration we focus on was studied in this context, and the possibility of metrological gain was demonstrated experimentally for two different interferometric configurations [6,7,15,25]. On the theoretical level, however, it is interesting to prove and explain which configuration is the most optimal one, i.e.…”

Many-body effects in quantum metrology

“…The research effort in the field of quantum metrology [1][2][3][4] goes along two main directions. The first is the experimental one, with the ultimate goal of designing metrological setups that harness quantum behavior of light and matter while at the same time minimize unwanted effects of decoherence in order to reach the precision regime inaccessible within the classical paradigm [5][6][7][8][9]. The theoretical effort, on the other hand, aims at identifying new promising proposals for quantum metrological protocols as well as fundamental bounds on precision that can in principle be achieved in quantum systems.…”

Non-Markovian effect on quantum optical metrology under a dissipative environment

“…It is wellknown that the enhanced precision due to the quantum effects can go far beyond their classical counterparts. In recent years, quantum metrology has been widely used in various directions such as gravitational wave detection [12], radar [13], magnetic field sensing [14][15][16][17][18][19], atomic clocks [20][21][22]. It also exhibits far-reaching impacts on quantum imaging [23][24][25], optical lithography [26], quantum information [27], quantum biology [28][29][30], etc.…”