Optical clocks are amazingly stable frequency standards, which would be off by only one second over the age of the universe. Bringing those clocks from the laboratory into a robust and compact form will have a large impact on telecommunication (e.g. network synchronization, traffic bandwidth, GPS free navigation), geology (e.g. underground exploration, monitoring of water tables or ice sheets), astronomy (e.g. low-frequency gravitational wave detection, radio telescope synchronization), and other fields. Likewise, techniques developed for robust clocks will improve laboratory clocks, potentially leading to physics beyond the standard model.
At the University of Birmingham, we help realising a compact and transportable strontium-based optical atomic clock demonstrator built from industry-developed subsystems – a deliverable of the iqClock project. The demonstrator will be integrated at our laboratory. In order to facilitate the system integration, we use an atomic clock testbed system to assess the performance of the industry-built components and subsystems. The testbed is completed in its first phase (see picture) and capable of realising ultra-cold atoms of 88Sr in optical lattice. In a subsequent phase, we will transform the testbed system into a 87Sr-based frequency standard.
Testbed setup with lattice beam and clock beam in vertical direction
Optical atomic clocks, frequently referred to as "quantum clocks", can provide timing with unprecedented accuracy and stability with improvements of several orders of magnitude when compared to any currently available commercial clock. In order to harness the extreme accuracy and stability for timing and communication infrastructure, the output signal needs to be converted as loss-less as possible into signals commonly used in telecommunication networks.
To address this challenge, in IQ-CLiK – a joint project between BT, Chronos Technology, and the University of Birmingham - we investigate the performance of a clock-to-network interface in conjunction with a state-of-the art transportable optical atomic clock and a telecom fibre link of several kilometres of length. Additional modelling of sub-nanosecond quantum clock-assisted time dissemination will allow us to understand the scalability and costs involved in integrating such technology into national timing and communication infrastructure. Hence, our project IQ-CLiK will help guiding the way to using optical atomic clocks in communication networks to provide improved network timing precision.
Frequency comb which is used in telecommunications and network synchronisation
Spectrum of the low-noise supercontinuum spectrum spanning greater than one octave
Network synchronisation better than 1ns using a frequency comb
Optical frequency combs are a valuable technology for network synchronisation and many other applications. They are commercially available from only a few vendors, none of whom are in the UK. In this project, we aim to make a feasibility study on developing a new method for generating optical frequency combs using a mode-locked femtoseond laser and novel photonic crystal fibre. These will be combined to generate a theoretically fully coherent method for supercontinuum broadening, thereby transferring the excellent noise performance of the mode-locked laser into an octave-spanning optical frequency comb. Research will be needed to understand the remaining noise and how it can be reduced, and here we will investigate both frequency jitter reduction and absolute frequency stabilisation to further minimise the noise and prepare it for use in a telecommunications system, holding timing, and thereby keeping track of the great swaths of data transmitted in and out of the UK daily.
The Long Range Interaction project
This project aims to characterise and study long-range interactions with collective light scattering from a dense, ultracold Sr atomic ensemble trapped in deep optical lattice in a Mott insulator state. Such long range dipole-dipole interactions between atoms are induced via coherent exchange of photons when the inter-atomic distance is comparable to or smaller than the wavelength of the photons emitted by atoms.
In order to attest the dipolar interactions in the experiment, the Sr atoms are initially trapped in the MOT , and then transferred to an optical dipole trap for preparing a dense ultracold Sr atomic ensemble. The atoms will then be loaded in a 3D optical lattice and finally to a Mott insulator state. Once the atoms are loaded, the detection of long-range interactions can be facilitated with 2.6 µm laser as a probe. The Sr system provides an alternative platform to study long-lived collective states, opening pathways for potential applications in quantum information processing.
Assembly of ultra-high vacuum and science chamber
SOC-2; Space Optical Clock – II [Link]
Today we use atomic clocks and strive for always higher precision levels to be achieved with new quantum technologies, in particular optical ones. The use of atomic clocks in space is a new challenge, which the SOC2 project takes on by developing compact and reliable designs.
The Quantum Enabled Radar project
Most radar systems are built for the purpose of detection and sensing of targets. Today, with the increasing complexity of the real world, we have to operate radars under challenging conditions such as high clutter urban environments and external interference. These conditions reduce the detection capability of radar systems. The quantum enabled radar network has the potential to overcome a lot of these issues with the use of technologies such as ultra-stable quantum oscillators to improve the phase noise of the radar’s local oscillator by orders of magnitude and enhance the sensitivity of the radar.
Schematics of the LRI experiment
Aveillant L-band staring radar on campus
In various applications such as modern communications, gravitational wave detection, metrology, development of quantum technologies such as atom trapping as well as time keeping is rapidly growing. Fibre optic is used in transmitting the light in such systems. However, due to variation in temperature, pressure, mechanic stretch in the fibre, a noise is introduced to the laser beam that passes through the fibre. This is considered as one limiting factor in many experimental settings that use fibre optic.
Schematics of basic fibre noise cancellation system
MoSaiQC: Modular Systems for Advanced Integrated Quantum Clocks [Link]
The unprecedented control over cold atoms has resulted in an extremely precise measurement of time and frequencies. In our lab, we work on enabling concepts through to asking very fundamental questions at the cutting edge of science. We have PhD positions within the EU-ITN-MoSaiQC to train a cohort of young scientists at the frontiers of physics. The PhDs will work on cutting edge projects developing novel concepts relevant to metrology and fundamental science. They will have access to our state-of-the-art labs and will also benefit from the European Collaborations as well as from our direct link to the UK National Quantum Technology Hub in Sensors and Metrology
For this a noise free fibre with long-time stability is needed in application such as quantum technologies. The vision of this work is to develop a system that can compensate for the noise and vibration in the optical fibre with a stability of 10-17. The project also aims to achieve the feasibility of world class noise cancellation while delivering a more integrated system, resilient and better suited to end user applications. Our team is working with M Squared Lasers to realise a cost effective, compact and good performance commercial fibre noise cancellation product.
FACT – Future Atomic Clock Technologies, EU Marie Curie ITN network with 14 partners. [Link]
QTEA – Quantum Sensor Technologies and Applications, EU ITN Network. [Link]
SLATE: Strontium Lattice for Commercial Optical Clocks [Link]
DPSS Laser stabilised at 813nm for Sr Clock Application [Link]
Miniature Optical Lattice Clock
Strontium Optical LAttice Clock (SOLACE) [Link]
Compact optics for high performance portable atomic timing and quantum sensors [Link]