Work Package 6

Ultrafast all optical spin control in quantum dots without magnetic fields

Summary: 

The group led by SOLID partner Jonathan Finley at the Walter Schottky institut of TUM achieve fast, all optical spin control in a single quantum dot without magnetic fields...

In a recent publication in Scientific Reports the group led by SOLID partner Jonathan Finley at the Walter Schottky institut of TUM achieve fast, all optical spin control in a single quantum dot without magnetic fields.

Superconducting qubits detect strain tuning of individual atomic tunnelling systems...

Summary: 

SOLID group at KIT demonstrate strain tuning of individual atomic tunelling systems detected by a superconducting qubit...

In their recent article in Science Magazine the SOLID group at KIT led by Alexey Ustinov demonstrated experimentally that minute deformation of the oxide barrier changes the energies of the atomic tunneling systems, and measured these changes by microwave spectroscopy of the superconducting qubit through coherent interactions between these two quantum systems.

Partial-Measurement Backaction in a Superconducting Circuit...

Summary: 

TU Delft group realize indirect partial measurement of a transmon qubit in circuit quantum electrodynamics by interaction with an ancilla qubit and projective ancilla measurement with a dedicated readout resonator. 

In a recent publication in Physical Review Letters the TU-Delft group led by SOLID partner Leo DiCarlo demonstrated an indirect partial measurement of a transmon qubit in circuit quantum electrodynamics.  This was don by interaction with an ancilla qubit and projective ancilla measurement with a dedicated readout resonator. Accurate control of the interaction and ancilla measurement basis allowed the group to show how it is possible to tailor the measurement strength and operator.

Near unity efficiency nanowire single photon sources...

Summary: 

By embedding quantum dots within tapered nanowires the TU-Delft team demonstrated near unity efficiencies for single photon generation...

In a recent publication in Nature Communications the TU-Delft team including SOLID partner Leo Kouwenhoven demonstrated a semiconductor nanowire based single photon source with a near unity efficiency.  To do this, the group positioned single quantum dots on the axis of a tailored nanowire waveguide using bottom-up growth.

Spin charge relaxation in double quantum dots...

Summary: 

SOLID collaboration reveals spin charge relaxation

IThe SOLID group of Lieven Vandersypen recently published a paper in Physical Review Letters in which they investigated phonon-induced spin and charge relaxation mediated by spin-orbit and hyperfine interactions for a single electron confined within a double quantum dot. They extract an electron spin relaxation rate that varies nonmonotonically with the detuning between the dots and confirm this model with experiments performed on a GaAs double dot.

Quantum heating of non-linear resonators...

Summary: 

quantum heating

The Quantronics group at SOLID partner CEA have recently published a paper in Physical Review Letters in wihch they measure the quantum fluctuations of a pumped nonlinear resonator using a superconducting artificial atom as an in situ probe. The qubit excitation spectrum provided access to the frequency and amount of excitation of the intracavity field fluctuations, from which we infer its effective temperature.

Giant cross Kerr effects...

Summary: 

Giant cross-Kerr effects for propagating microwaves induced by an artificial atom

The Chalmers team led by Chris Wilson recently published a paper in Physical Review Letters in which they investigated the effective interaction between two microwave fields, mediated by a transmon-type superconducting artificial atom that is strongly coupled to a coplanar transmission line. The interaction between the fields and atom produces an effective cross–Kerr coupling.

Breakdown of the cross-Kerr scheme for photon counting...

Summary: 

Breakdown of the cross Kerr scheme for photon counting

The Chalmers SOLID group recently published an article in Physical Review Letters in which they show, in the context of single-photon detection, that an atomic three-level model for a transmon in a transmission line does not support the predictions of the nonlinear polarizability model known as the cross-Kerr effect.

Coherence at a distance...

Summary: 

Long distance coherent coupling in a quantum dot array

The group led by Lieven Vandersypen at TU-Delft recently published a paper in Nature Nanotechnology in which they show that two distant sites in an electrostatically defined quantum dot array can be tunnel-coupled directly. The coupling is mediated by virtual occupation of an intermediate site, with a strength that is controlled via the energy detuning of this site.

Entanglement by measurement in diamonds...

Summary: 

Hanson group demonstrate entanglement by measurement in solid state qubits...

In a recent publication in Nature Physics the group led by SOLID partner Ronald Hanson realized a two-qubit parity measurement on nuclear spins localized near a nitrogen-vacancy centre in diamond by exploiting an electron spin as a readout ancilla. The measurement enabled the group to project the initially uncorrelated nuclear spins into maximally entangled states.

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