News

27/06/2019 - We started the baking of our oven 9 days ago, and we managed to successfully bake the oven!

18/01/2019 - New publication:"Population dynamics in sideband cooling of trapped ions outside the Lamb-Dicke regime". We present the results of simulations of optical sideband cooling of atomic ions in a trap with a shallow potential well. In such traps, an ion cannot be Doppler cooled near to the Lamb-Dicke regime $[{\mathrm{\eta 2}}^{}(2⟨n⟩+1)\ll 1]$. Outside the Lamb-Dicke regime, the sideband cooling dynamics are altered by the existence of various Fock states with weak coupling where the cooling becomes very slow. A ⁴⁰Ca⁺ ion trapped in our Penning trap realizes such a situation; hence single stage cooling is inefficient to prepare the ion in the motional ground state. For these systems, it is necessary to study the cooling dynamics in detail and we show that it is possible to implement an optimized cooling sequence to achieve efficient ground-state cooling. We also present the simulated cooling dynamics of two ions trapped in a Penning trap, where the presence of an additional motional mode requires a complicated cooling sequence in order to cool both axial modes to the ground state simultaneously. Additionally, we demonstrate the dissipative preparation of Fock states outside the Lamb-Dicke regime by sideband heating a single ion in a Penning trap.

15/10/2018 - We welcome Yohannes to the ion trapping research group!

01/10/2018 - We welcome Simon to the ion trapping research group!

15/09/2018 - We would like to congratulate Manoj Joshi, Pavel Hrmo and Vincent Jarlaud for completing their PhD!

10/07/2018 - New publication: "Trapped-ion quantum error-correcting protocols using only global operations". In this paper, we have studied the formation and properties of two-species ion Coulomb crystals in the Penning trap of the SpecTrap experiment. These crystals have been formed by injection of admixture ions from an external source into a previously confined and laser-cooled cloud of magnesium ions. This kind of study, performed over a range of the admixture ions’ charge-to-mass ratios, indicates the conditions for their sympathetic cooling and the formation of two-species ion crystals. This mechanism allows efficient cooling of the admixed species such as highly charged ions which do not feature suitable laser-cooling transitions, and thus make them accessible to high-resolution laser spectroscopy.

29/08/2017  The ion trap group at Imperial College London has two vacancies for postdocs (one theory, one experiment).  These positions are associated with a new research grant on optimal control in ion traps, with Richard Thompson and Florian Mintert as co-investigators.  See our website  or email Professor Richard C.. Thompson or Professor Florian Mintert for more information.  The closing date is 21st September 2017.

01/8/2017 -  Our new research grant from EPSRC entitled “Optimal Control for Robust Ion Trap Quantum Logic” starts.  This grant will support a collaboration between Richard Thompson (Experiment) and Florian Mintert (Theory) for 4 years. Click here for the link for the grant proposal.

27/08/2016 - On Wednesday 16th March 2016, a celebration of the life of our friend and colleague Danny Segal took place. There was a session of talks, followed by an evening of music. Videos from the event can be found here.

06/04/2016 - New publication: "Resolved-Sideband Laser Cooling in a Penning Trap". In this paper we report the cooling the axial motion of a single calcium ion to its quantum ground state using resolved-sideband laser cooling. This is the first time that this has been achieved in a Penning trap and has particular importance to the field of precision measurement, where this type of trap is widely used. We have also measured the motional heating rate in our system and have found it to be lower than any previously reported figure.

29/02/2016 - Congratulations to Graham Stutter on passing his PhD viva!

11/09/2015 - New publication: "Trapped-ion quantum error-correcting protocols using only global operations". In this paper, we propose an experiment that uses only global operations to encode information to either the five-qubit repetition code or the five-qubit code on a two-dimensional ion Coulomb crystal architecture. We show that we can prepare, read out, and acquire syndrome information for these two codes by using only six and ten global entangling pulses, respectively. We provide an error analysis, estimating we can achieve a sixfold improvement in coherence time with as much as 1% noise in the control parameters for each entangling operation.

27/02/2015 - Congratulations to Joe Goodwin on passing his PhD viva!

07/03/2014 - New publication: "Optical sideband spectroscopy of a single ion in a Penning trap". In this paper, we show that the parameters of the radial laser-cooling beam determine the rotation frequency of a small crystal in a Penning trap when no driving fields are present. We demonstrate, using an approximate theoretical treatment and realistic simulations, that the crystal rotation frequency is independent of the number of ions and the trap parameters, so long as the crystal radius remains smaller than the cooling laser beam waist. As the rotation frequency increases, the crystal eventually becomes a linear string, at which point it is no longer able to adjust its density. Instead, a small amplitude vibration in the zigzag mode of oscillation manifests itself as a rotation of the crystal at a fixed frequency that depends only on the applied trap potential.

05/11/2013 - New publication: "Theory and simulation of ion Coulomb crystal formation in a Penning trap". In this paper we develop a theoretical model for the formation of small ion Coulomb crystals (ICCs) in a Penning trap, when the ions are subject to a radial laser cooling beam. We show that the rotation speed of the ICC is determined mainly by the parameters of the laser beam and not the trap, so long as the radial extent of the crystal is less than the diameter of the laser beam. This result has been confirmed by simulations of the system that take into account all the forces acting on the ions, including the trapping forces, the Coulomb interaction of the ions, and the interaction with the cooling laser beam.

07/10/2013 - New publication: "Control of the conformations of ion Coulomb crystals in a Penning trap". In this paper we report new images of an exotic state of matter formed by atomic ions that are held in a device called a Penning ion trap. The calcium ions are trapped by a combination of electric and magnetic fields and stay in the trap for hours at a time. They are slowed down till they are virtually stationary by a process of "laser cooling" where they are bathed in laser light at a very precisely known frequency. Once they are cold they arrange themselves in different configurations depending on the strength of the trapping fields. These "ion Coulomb crystals" are very similar to tiny conventional crystals like diamond except that the distance between the ions here is about 100 000 times bigger than the distance between atoms in a conventional crystal, so the density of the ion crystal is extremely low - roughly the same as the ultra-high vacuum inside the trap. The ion crystals can be photographed by a sensitive digital camera and we can manipulate the trapping fields to change the ion crystal shape from a linear string of ions through many different three-dimensional structures to a pancake-like crystal. All of these configurations can be reproduced in simulations. Ion Coulomb crystals have been observed and studied before in different sorts of ion trap but our research represents the most detailed study of all the different structures that are possible at this tiny scale. This work has potential applications in the area of "Quantum Simulation", where systems of atoms or ions are used to simulate quantum processes that cannot be studied using conventional computers.

18/07/2013 - We have a new website!!!