Nam Nguyen and Nadia Antoniadis both receive the QCQT Excellence Award 2023. Nam got it in recognition of his outstanding work in the publications “Enhanced Electron-Spin Coherence in a GaAs Quantum Emitter” published in PRL and  “Quantum interference of identical photons from remote GaAs quantum dots” published in Nat. Nanotechnol. Nadia got the price for her outstanding work in “Cavity-enhanced single-shot readout of a quantum dot spin within 3 nanoseconds” published in Nat. Commun. and “A chiral one-dimensional atom using a quantum dot in an open microcavity” published in npj Quantum Inf. Congratulations!!

Andrea Corazza receives two poster awards: the 2023 MRS Fall Meeting Best Poster Award and the EL14 Diamond Electronics, Devices and Sensors Best Poster Award 2023 for the poster “Diamond defects: a Gateway to Spin-Photon Interfaces”. Congratulations!

In our recent publication in Physical Review Letters, we increased the coherence of an electron spin in a GaAs quantum dot to over half a microsecond. This 150-fold improvement is achieved by using the interaction of electron spins and nuclear spins to cool the spin system. More information can be found on the SNI news.

Our latest results on ultra-fast cavity-enhanced single-shot readout of a quantum dot electron spin in 3 nanoseconds have been published in Nature Communications.

In our recent publication in Nature Physics, we directly observe a photon number dependent time-delay upon scattering of a laser pulse. This is a fingerprint of simulated emission at the level of a few photons. More information can be found in the Uni news.

Simon Geyer is selected as APS Distinguished Student (DS) for outstanding non-US young researchers. He received his prize at the APS March meeting 2023.
Congratulations!!

Clemens Spinnler receives a QCQT 2022 Excellence Award in recognition of his outstanding work to “Optically driving the radiative Auger transition”, published in Nature Comm. and “Quantum interference of identical photons from remote GaAs quantum dots” published in Nature Nano. Congratulations!!

In our most recent manuscript, published in Applied Physics Letter, we present an improved method for the creation of narrow-linewidth nitrogen-vacancy centers (NVs) in microstructured diamond. NVs are known for their exceptional spin coherence and convenience in optical spin initialization and readout, and are increasingly used both as a quantum sensor and as a building block for quantum networks. The standard method relying on nitrogen implantation to create NVs tends to create NV populations with broadened optical linewidth. The phenomenon is much aggravated when photonic structures allowing a better photon collection efficiency are created around the emitters. We demonstrate that implantation of carbon ions yields a comparable density of NVs as implantation of nitrogen ions, and that implantation after instead of before the diamond fabrication process results in NV populations with narrow optical linewidths and low charge-noise levels even in thin diamond microstructures. We measure a median NV linewidth of 150 MHz for structures thinner than 5 μm, with no trend of increasing linewidths down to the thinnest measured structure of 1.9 μm and confirm our results in multiple samples implanted with different ion energies and fluences.

Natasha Tomm has received two awards for her PhD thesis “A quantum dot in a microcavity as a bright source of coherent single photons” this year!

The first prize was the Prix Schläfli in Physics 2022, awarded by the Swiss Academy of Sciences (SCNAT). The Prix Schläfli is one of the oldest prizes in Switzerland and awards every year the best dissertations in natural sciences. Read more here.

The second one was given by the Philosophisch-Naturwissenschaftliche Fakultät of the University of Basel. Every year the Faculty awards two outstanding dissertations that have demonstrated great importance and quality of the scientific contributions.

Congratulations!!!

In our recent publication in Physical Review Letters, we experimentally and theoretically study exciton-exciton couplings in a two-dimensional semiconductor, homobilayer MoS₂. More information can be found in the SNI news or in this short explanation video.

Simon Geyer was recognized with the Swiss Nanotechnology PhD award sponsored by the IBM Research Zürich for the publication “A hole spin qubit in a fin field-effect transistor above 4 kelvin”. Congratulations!!

Recently published in Nature Nanotechnology, we demonstrate quantum interference between single photons from separate quantum dots. Such a demonstration has been attempted multiple times in the past decade and appeared challenging. The problem is the noise: the noise affects the photon creation process of different quantum dots in different ways. Thus, single photons created by separate quantum dots are sometimes distinguishable. Low-noise GaAs quantum dots are employed for our work, each operated in an independent cryostat. Single photons are created from two distant quantum dots and simultaneously sent to two inputs of a beamsplitter. Despite their (different) origins, the photons exhibit bunching in the beamsplitter output with 93% visibility: they are almost identical. Using an optical CNOT operation, we achieve high-fidelity entanglement between photons from two quantum dots. Our results establish low-noise GaAs quantum dots as interconnectable sources of identical photons.

In out recent publication in Journal of Applied Physics, we report on an open microcavity containing a diamond micromembrane. Despite operation in the so-called diamond confined regime, where the electric field profile inside the cavity is maximized across the diamond-air interface, we demonstrate quality factors exceeding 120 000. We next develop a qualitative model describing the losses in our cavity and determine that the dominant source of losses to be surface waviness – surface textures with dimensions comparable to the cavity beam waist. The large quality factor combined with a small mode volume of 3.9λ₀³, yield a predicted Purcell factor of 170, a significant improvement over the state-of-the-art.

In our recent publication in npj Quantum Information we have demonstrated a chiral one-dimensional atom using a single semiconductor quantum dot in a tunable microcavity. In a chiral atom, photons propagating in one direction interact with the atom, while photons propagating in the other direction do not. Here, we achieve strong non-reciprocal absorption of single-photons, a single-photon diode. Proof that chirality arises from a single emitter is found in the nonlinear behaviour at low powers – light propagating in the backward direction of the diode is highly bunched.

One of the greatest challenges in quantum computing is scalability. Classical computing overcome this problem by integrating bilions of nm-scale fin field-effect transistors (FinFETs) on a silicon chip. Here, we operate a silicon FinFET as a hole spin qubit above 4 K. At this elevated temperature cooling power increases by order of magnitudes compared to typical qubit operation temperatures, such that on-chip integration with control electronics becomes feasible. We achieve fast electrical 3-axis control with speeds up to 150 MHz, single-qubit fidelities at the fault-tolerance threshold, and a Rabi quality factor greater than 87. The devices feature both industry compatibility and quality, yet are fabricated in a flexible and agile way accelerating future development. The work was published in Nature Electronics.

Prof. Richard Warburton received the prestigious Nevill Mott Medal and Prize from the Institute of Physics (UK)! The prize was awarded in recognition of his outstanding research in solid-state physics and quantum optics, especially the invention and application of Coulomb blockade devices to create coherent spin-photon interfaces and quantum light sources. Congratulations!

Read more here: https://www.iop.org/about/awards/2021-nevill-mott-medal-and-prize

Radiative Auger is a process that leads to red-shifted satellite peaks in the emission of atoms and solid-state quantum emitters. It is caused by Coulomb interactions between charged carriers. In our recent paper in Nature Communications, we show for the first time that it is possible to turn the whole process around by optical driving of the radiative Auger transition. Possible applications could be fast optical switching or THz spectroscopy.

Nadine Leisgang was recognized with the Swiss Nanotechnology PhD award sponsored by the Hightech Zentrum Aargau for the publication “Giant Stark splitting of an exciton in bilayer MoS₂”. Congratulations!!

Read more here: https://nanoscience.ch/en/2021/08/09/excellent-prizes-for-outstanding-doctoral-students/

Nadine Leisgang received the Nano Image Award 2021 for the optical micrograph image of a gated van der Waals heterostructure. The device consists of two monolayers of transition metal dichalcogenides encapsulated between insulating hexagonal boron nitride flakes. Direct gold contacts allow tuning the carrier concentration in the optically active layers in the middle of the structure. Few-layer graphene sheets on the top and bottom of the stack serve as local gates to apply an electric field across the device.

This image reflects the complexity and – at the same time – the beauty of the fabrication of van der Waals heterostructures.

In our recent publication in ACS Photonics, we report on the pulsed-laser-induced generation of high-quality nitrogen-vacancy (NV) centers in diamond facilitated by a solid-immersion lens (SIL). The SIL enables laser writing at energies as low as 5.8 nJ per pulse and allows vacancies to be formed close to a diamond surface without inducing surface graphitization. We present samples in which NV center arrays were laser-written across the full diamond thickness, all presenting narrow optical linewidth distributions with means down to 62.1 MHz. The linewidths include the effect of long-term spectral diffusion induced by a 532 nm repump laser for charge-state stabilization, underlining the extremely low charge-noise environment of the created color centers.