PhD Studentship in Photonic Quantum Gates (2018)

A fully funded 3.5 year PhD position is available in the Ion Trap Cavity-QED and Molecular Physics (ITCM) Group in the Department of Physics & Astronomy at the University of Sussex.

Entanglement is at the heart of quantum information processing. Up to 14 qubits have been entangled in ion strings [1] using collective phonon excitations. An alternative to the vibrational coupling of ions is provided by photons. By analogy with phonon-based gates, the internal states of ions can be entangled with the states of photons, which in turn can establish a long-range interaction between ions in the string. To enhance the coupling between ions and single photons, a high-finesse optical cavity is required [2]. In this setting, gates between arbitrary ions coupled to the cavity mode can be realized [3]. The goal of the project is the first implementation of a photon-based gate for ion qubits. In the Ion-Trap Cavity-QED group, we have set up a miniature trap-cavity system optimized for strong ion-photon coupling. A linear ion trap is combined with an optical cavity whose axis is orthogonal to that of the trap (Fig. 1). In this way, any ions in a string interacting with the cavity field can be coupled (see Fig. 2). Which ions participate in a quantum gate is controlled by addressing them with a laser injected from the top. The simplest gate to realize entangles two ions in the cavity through the partial exchange of a single photon. Initially, one ion is prepared in the ground state, the other in a metastable state. As soon as coupling to the cavity is established, the ions perform a cavity-assisted Rabi-oscillation via the Raman transition connecting the two states. Stopping the Rabi-oscillation after a p/2-pulse, each ion is in a superposition of the two basis states such that the state of the system is entangled. The entanglement must be verified and quantified. Entangled states respond to qubit-rotations in a characteristic way, so that the amount of entanglement can be estimated. More complex gates are possible by making use of the Zeeman substructure of calcium ions.

[1] T.Monz et al., Ph.Rev.Lett. 106, 130506 (11).

[3] M. Feng, Phys. Rev. A 66, 054303 (2002).

[2] M. Keller et al., Nature 431, 1075 (2004).

Type of award

Postgraduate Research


£14,553 (2017-18) per year tax-free bursary plus the waiver of UK/EU fees each year for 3.5 years. Full-time study.


Applicants should hold, or expect to hold, a UK undergraduate degree in physics or a related subject. Due to funding restrictions, the studentship is open to UK and EU resident students only. However, we also welcome applications from self-funded non-EU students.


1 March 2018 23:59 (GMT)

How to apply

Online applications at:

State in the Funding section of the application form that you are applying for the "PhD Studentships in Experimental Atomic Physics".


The award includes an additional training grant of £1650 p.a. for short courses, books, travel. conferences etc.

Additional funding may also be available to support placements with outside partners for a further period of six months in total.

Contact us

For further information about the project, please get in touch with Prof Matthias Keller.

For practical questions about the application process and/or eligibility for funding, please contact:


Application deadline: 1st March 2018

Start date: September 2018

Early application is advised. The studentship will be allocated as soon as a suitable candidate is found.


At level(s):
PG (research)

Application deadline:
1 March 2018 23:59 (GMT)
the deadline has now expired