5 research outputs found
Towards mobile quantum sensors for gravity surveys
Design and first characterisations of the mobile sensor head in the Gravity Gradient Technologies and Opportunities Programme (GGtop) are presented. The aim of the project is the development of a mobile gravity gradiometer and faces the challenge of condensing a normally lab filling experiment in a portable and robust package. A fibre network replaced free space optics light distribution and fibre based components free space equivalents. Although stable against misalignment, the systems performance is limited by polarization changes of the guided light which arise from birefringence fluctuations along the length of the network due to external temperature fluctuations and mechanical disturbances. These instabilities limit the achievable temperature of the trapped rubidium 87 cloud to approx. 18μK. In preparation for gravity measurements, Rabi oscillations and Ramsey fringes with a λ/2 time of 7.4μs were successfully demonstrated in a co-propagating Raman beam configuration. The atom cloud was launched as a first step towards gravity gradiometry. As the system was designed to be portable, the complete system fits into a 1.5m x 2m x 0.5m package, plus a 14u rack of support electronics
Application of optical single-sideband laser in Raman atom interferometry
A frequency doubled I/Q modulator based optical single-sideband (OSSB) laser
system is demonstrated for atomic physics research, specifically for atom
interferometry where the presence of additional sidebands causes parasitic
transitions. The performance of the OSSB technique and the spectrum after
second harmonic generation are measured and analyzed. The additional sidebands
are removed with better than 20 dB suppression, and the influence of parasitic
transitions upon stimulated Raman transitions at varying spatial positions is
shown to be removed beneath experimental noise. This technique will facilitate
the development of compact atom interferometry based sensors with improved
accuracy and reduced complexity
Experimental Comparison of Efficient Tomography Schemes for a Six-Qubit State
Quantum state tomography suffers from the measurement effort increasing
exponentially with the number of qubits. Here, we demonstrate permutationally
invariant tomography for which, contrary to conventional tomography, all
resources scale polynomially with the number of qubits both in terms of the
measurement effort as well as the computational power needed to process and
store the recorded data. We demonstrate the benefits of combining
permutationally invariant tomography with compressed sensing by studying the
influence of the pump power on the noise present in a six-qubit symmetric Dicke
state, a case where full tomography is possible only for very high pump powers.Comment: 7 pages, 7 figure
A portable magneto-optical trap with prospects for atom interferometry in civil engineering
The high precision and scalable technology offered by atom interferometry has the opportunity to profoundly affect gravity surveys, enabling the detection of features of either smaller size or greater depth. While such systems are already starting to enter into the commercial market, significant reductions are required in order to reach the size, weight and power of conventional devices. In this article, the potential for atom interferometry based gravimetry is assessed, suggesting that the key opportunity resides within the development of gravity gradiometry sensors to enable drastic improvements in measurement time. To push forward in realizing more compact systems, techniques have been pursued to realize a highly portable magneto-optical trap system, which represents the core package of an atom interferometry system. This can create clouds of 10
7
atoms within a system package of 20 l and 10 kg, consuming 80 W of power.
This article is part of the themed issue ‘Quantum technology for the 21st century’.</jats:p
Permutationally invariant state reconstruction
Feasible tomography schemes for large particle numbers must possess, besides
an appropriate data acquisition protocol, also an efficient way to reconstruct
the density operator from the observed finite data set. Since state
reconstruction typically requires the solution of a non-linear large-scale
optimization problem, this is a major challenge in the design of scalable
tomography schemes. Here we present an efficient state reconstruction scheme
for permutationally invariant quantum state tomography. It works for all common
state-of-the-art reconstruction principles, including, in particular, maximum
likelihood and least squares methods, which are the preferred choices in
today's experiments. This high efficiency is achieved by greatly reducing the
dimensionality of the problem employing a particular representation of
permutationally invariant states known from spin coupling combined with convex
optimization, which has clear advantages regarding speed, control and accuracy
in comparison to commonly employed numerical routines. First prototype
implementations easily allow reconstruction of a state of 20 qubits in a few
minutes on a standard computer.Comment: 25 pages, 4 figues, 2 table