J. Nilsson

An entangled-LED-driven quantum relay over 1 km

Each datafile corresponds to a figure dataset in the paper. For figures 2c, 3, 4a & 4b the two time axes are given as the top row (X-values) and first column (Y-values). Data format for these is as follows: Y values accross columns and X values accross rows. In figure 4a, undefined fidelity points are indicated by value -0.5. For figures 3a, b, c & d, the two columns are separated as: e.g. figure3a_exp (for experimental data) and figure3a_sim (for simulated data).

Few-second-long correlation times in a quantum dot nuclear spin bath probed by frequency-comb nuclear magnetic resonance spectroscopy

Using a frequency-comb nuclear magnetic resonance spectroscopy technique it is possible to probe the fluctuations in the nuclear spin bath of a self-assembled quantum dot and reveal long nuclear spin correlation times over one second.

Voltage control of electron-nuclear spin correlation time in a single quantum dot

We demonstrate bias control of the hyperfine coupling between a single electron in an InAs quantum dot and the surrounding nuclear spins monitored through the positively charged exciton X+ emission. In applied longitudinal magnetic fields we vary simultaneously the correlation time of the hyperfine interaction and the nuclear spin relaxation time and thereby the amplitude of the achieved dynamic nuclear polarization under optical pumping conditions. In applied transverse magnetic fields a change in the applied bias allows to switch from the anomalous Hanle effect to the standard electron spin depolarization curves.

Quantum key distribution with an entangled light emitting diode

Measurements performed on entangled photon pairs shared between two parties can allow unique quantum cryptographic keys to be formed, creating secure links between users. An advantage of using such entangled photon links is that they can be adapted to propagate entanglement to end users of quantum networks with only untrusted nodes. However, demonstrations of quantum key distribution with entangled photons have so far relied on sources optically excited with lasers. Here, we realize a quantum cryptography system based on an electrically driven entangled-light-emitting diode. Measurement bases are passively chosen and we show formation of an error-free quantum key. Our measurements also simultaneously reveal Bells parameter for the detected light, which exceeds the threshold for quantum entanglement.

Teleportation using a quantum dot entangled-light-emitting diode

We demonstrate for the first time teleportation mediated by electrically generated entangled photon pairs emitted by a quantum dot based entangled-light-emitting diode (ELED) [1]. Apart from being a striking manifestation of entanglement, teleportation also underpins several quantum information applications, such as the realization of near-deterministic quantum logic [2] and the formation of secure quantum networks over long distances [3].

Electrically generated indistinguishable and entangled photon pairs

We present measurements on electrically generated photons from a quantum dot in an LED structure, showing high entanglement fidelity and two-photon interference visibility, both necessary requirements for scalable quantum communication and logic.