Each month we will invite guest speakers with the intention of maintaining and promoting network interactions between the annual meetings. The webinars will typically take place on the first Thursday of the month at 3 pm UK time, subject to speaker availability.

2022 Program

Speaker: Jörg Wrachtrup, University of Stuttgart

Thursday 16th June 2022 at 3 pm (BST)
Title: Quantum Technology With Spins
Please click on the link to watch the recorded seminar

Spins in wide band gap semiconductors are a leading contender in various areas of quantum technology. Most notably they have been established as a novel tool for nanoscale sensing, major hardware for long distance quantum entanglement, as well as small scale quantum registers for quantum computing. I will present the use of spins in in those areas [1,2,3]. Specifically, I will discuss quantum sensing with spins to investigate magnetism in 2D materials including the investigation domain patterns [4] and Moiré structures in twisted 2D layers [5]. Here the nitrogen vacancy center in diamond is used to probe and image electronic magnetism in mono- and multilayers of materials like CrBr3. By using dedicated measurements strategies based on quantum algorithms one can enhance the performance of those quantum sensors to achieve better signal quality and improve the spectral resolution in those measurements. [6].

[1] T. Oeckinghaus et al., Nano Lett. 20, 463 (2020)

[2] N. Morioka et al. Nature Com. 2516 (2020)

[3] N. Chejanovsky et al. Nature Mat. 20, 1079 (2021)

[4] Qi-Chao Sun et al. Nature Com. 12, 1989 (2021)

[5] T. Son et al. Science 374, 1140 (2021)

[6] V. Vorobyov et al., njp Quantum Information 7, 124 (2021)

Speaker: Ed Bielejec, Sandia National Laboratory

Thursday 7th July 2022 at 3 pm (BST) check the time zone
Title: Overview of Sandia’s Ion Beam Capabilities: Focused Ion Beam Implantation
Please click on the link to watch the recorded seminar

We will present an overview of Sandia National Laboratories Ion Beam Laboratory’s (IBL) capabilities with an emphasis on focused ion beam implantation and irradiation.  The IBL operates seven focused ion beam (FIB) systems that range in ion energy from less than 1 keV to  greater than 70 MeV, including a wide range of ion species from protons to lead over a range of spot sizes from nm to mm.  In particular, we will concentrate on the development of our two mass filtered FIB systems, the A&D nanoImplanter and the Raith Velion, both of which include high spatial resolution with CAD based patterning to enable the formation of arbitrary patterned implantation.

The A&D nanoImplanter and the Raith Velion both run liquid metal alloy ion sources (LMAIS) and operate with nm scale resolution.  We will discuss the development of novel LMAIS for these systems which can currently run approximately one-third of the periodic table of elements including Li, N, Mg, Si, P, etc…  This combined with high resolution laser interferometry driven stages allow for the fabrication of custom implanted ion arrays for cutting edge physics and quantum optics experiments.

At Sandia National Laboratories we have multiple projects involving solid-state defect centers including the development of NV sensing in diamond and new defect center creation in wide bandgap semiconductors such as SiC and GaN using FIB implantation.  A critical issue with these solid-state defect centers is that the yield of optically active defect centers with the correct charge state is low, typically 3-10%.  We will outline Sandia’s approach for the development of single ion implantation and detection capability in conjunction with a new in-situ photoluminescence capability that are designed to enable the deterministic formation of the optically active defect centers.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Speaker: Kai-Mei Fu, University of Washington

Thursday 4th August 2022 at 3pm (BST) check the time zone
Title: ZnO donor qubits: synthesis and isolation of single donors
Please click on the link to watch the recorded seminar

Abstract: Neutral shallow donors in ZnO, such as Al, Ga or In substituting for Zn, are promising candidates for solid-state spin qubits, where the qubit states are formed by the spin state of the electron bound to the donor impurity. The donor electron is optically coupled to the neutral-donor bound excitons with a high radiative efficiency due to the direct band gap of ZnO. Here we investigate donors formed by implantation and annealing and the isolation of single donors by microstructuring bulk ZnO. We show that ensembles of indium ZnO donors formed by implantation and annealing exhibit an inhomogeneous linewidth of < 10 GHz, on par with the best reported bulk ZnO samples. Donors emission is stable under resonant excitation indicating high charge stability. In nanostructured, bulk ZnO (in collaboration with the Pacific Northwest National Lab), we observe single indium donors with optically stable emission in both intensity and frequency.

Speaker: Margherita Mazzera, Heriot-Watt University

Thursday 3rd November 2022 at 3pm (GMT) check the time zone
Title: Pioneering platform for integrated quantum memories donor qubits: synthesis and isolation of single donors
Please click on the link to watch the recorded seminar

The coherent interaction between photons and atoms lays the bases of quantum information science, whose purpose is to open new possibilities for the transmission and the processing of information. It is crucial, e.g., for the realisation of quantum networks. Solid-state systems have emerged as promising platforms; more specifically rare earth ion doped crystals are one of the most interesting candidates. The implementation of quantum memory protocols in waveguide has the potential of opening further avenues towards scalable quantum information protocols using complex quantum photonic circuits on chip.

Our approach is based on fs-laser written waveguides (LWW) fabricated in an insulating crystal which has proven outstanding performances as interface between single photons and single atomic or spin excitations, i.e. Pr:YSO [1]. The new writing regime adopted gave, with respect to previous demonstration in the same material, sensibly smaller guiding modes, with diameter compatible with the core of telecom fibres, but lower insertion and bending losses. Given the simplicity and versatility of the fabrication, its unique 3D capability and the outstanding storage performance, the demonstration represented a change of paradigm in the quest for integrated quantum memories. We demonstrated that this integrated platform for the storage of quantum states of light [2], also enabled the storage of more than 100 spectro-temporal modes [3] and the storage of photonic entanglement in a fibre-integrated device [4]. However, much has to be demonstrated yet with this platform, e.g., the on-demand storage of single photons. One major problem is that the integrated storage devices might prove more prone to photonic noise due to light confinement, as the single photon inputs travel in the same spatial mode as the high intensity pulses used for on-demand storage and retrieval.

We propose here two alternative routes to overcome this problem and perform on-demand storage in waveguides. One is to implement a gradient echo memory [5]. This scheme relies on the manipulation of the spectral absorption profile of an atomic ensemble by means of static electric fields to efficiently absorb and coherently reemit a light pulse. The significant advantage of the compact design is that metallic contacts can be deposited very close to the waveguide (about 100 μm), thus enabling the electrical control of the atomic resonances with limited voltage and with negligible cross-talk between adjacent waveguides. The other strategy is to complement the most widely used storage protocol for multimode quantum storage, the atomic frequency comb [6], with the off-resonant cascaded absorption protocol [7], originally proposed for warm vapours featuring a ladder-type energy level scheme. We expect this combined protocol to enable the storage of broadband photons, thanks to the enhancement of the light-matter inteaction in waveguides, while not being affected by photonic noise, because of the large separation in frequency between the single photon input and the high power pulses for the on-demand storage.

Finally, I will also discuss how, being able to deterministically position the rare earth ions at specific sites, at distances closely related to the operating wavelengths, would allow us exploiting super- and sub-radiance mechanisms of the ordered ensembles to enhance or suppress the photon emission and the storage efficiency in a controllable fashion. Moreover, the potential of exploiting each single rare earth ion as an independently addressable single photon source would open new avenues for the scalable spatial multiplexing of local quantum processors.

[1] A. Seri et al, Phys. Rev. X 7, 021028 (2017) ; K. Kutluer et al, Phys. Rev. Lett. 118, 210502 (2017).

[2] A. Seri et al, Optica 5(8) (2018) 934
[3] A. Seri et al, Phys. Rev. Lett. 123 (2019) 080502
[4] J. V. Rakonjac et al, Science Advances 8 (2022) eabn3919

[5] M. Nilsson et al, Opt.Com. 247 (2005) 393
[6] M. Afzelius et al, Physical Review A 79 (2009) 052329
[7] K.T. Kaczmarek et al, Physical Review A 97 (2018) 042316

Speaker: Daniel Higginbottom, Simon Fraser University

Thursday 1st December 2022 at 4pm (GMT) check the time zone
Title: Building the quantum internet


Quantum processors have advanced rapidly and state-of-the-art devices now outperform classical supercomputers at specific contrived problems. However, practical quantum advantage to solve problems in chemistry, materials engineering, optimization, and drug discovery may lie beyond such chip-scale devices. Networking modular quantum processors is a path to quantum computing at scale, but network interconnects are a daunting challenge for many leading quantum computers. Silicon colour centres are a new quantum computing platform with a native optical network interface that can be integrated on-chip and networked with existing telecommunications infrastructure to form a large-scale‘ quantum internet’.