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Format: 2022-11-26
Format: 2022-11-26
Format: 2022-11-26
2013-11-22 09:24

Deterministic entanglement of superconudcting qubits by parity measurement and feedback

In a recent publication in Nature, the group led by Leo DiCarlo at SOLID partner TU-Delft have performed a time-resolved, continuous parity measurement of two superconducting qubits using the cavity in a three-dimensional circuit quantum electrodynamics architecture and phase-sensitive parametric amplification. Using postselection, the group managed to produce entanglement by parity measurement reaching 88 per cent fidelity to the closest Bell state. Incorporating the parity meter in a feedback-control loop, we transform the entanglement generation from probabilistic to fully deterministic, achieving 66 per cent fidelity to a target Bell state on demand. These realizations of a parity meter and a feedback-enabled deterministic measurement protocol provide key ingredients for active quantum error correction in the solid state.

(Jonathan Finley, 2013-11-22 09:24)
2013-11-22 09:18

Entanglement at room temperature in diamond

In a recent publication in Nature Nanotechnology, the group led by Jörg Wrachtrup experimentally demonstrated entanglement between two engineered single solid-state spin quantum bits (qubits) at ambient conditions. Photon emission of defect pairs reveals ground-state spin correlation. Entanglement (fidelity = 0.67±0.04) was proved by quantum state tomography. Moreover, the lifetime of electron spin entanglement was shown to be extended to milliseconds by entanglement swapping to nuclear spins. The experiments mark an important step towards a scalable room-temperature quantum device being of potential use in quantum information processing as well as metrology.

(Jonathan Finley, 2013-11-22 09:18)
2013-11-22 09:15

Wallraff group demonstrate deterministic quantum teleportation with feed-forward in a solid state system. 

In a recent Nature Paper the group of Andreas Wallraff at ETH Zürich have realized full deterministic quantum teleportation with feed-forward in a chip-based superconducting circuit architecture. Hereby, they used a set of two parametric amplifiers for both joint two-qubit and individual qubit single shot readout, combined with flexible real-time digital electronics.  They have been successful to teleport quantum states between two macroscopic systems separated by 6 mm at a rate of 104 s, exceeding other reported implementations. The low transmission loss of the superconducting waveguides used is likely to enable the range of this and other schemes to be extended to significantly larger distances, enabling tests of non-loc- ality and the realization of elements for quantum communication at microwave frequencies. The demonstrated feed-forward may also find application in error correction schemes. 

 

(Jonathan Finley, 2013-11-22 09:15)
2013-11-22 09:07

Wrachtrup group sense single remote nuclear spins

The SOLID group of J. Wrachtrup recently published a paper in Nature Nanotechnology in which they present the detection and identification of single and remote 13C nuclear spins embedded in nuclear spin baths surrounding a single electron spin of a nitrogen- vacancy centre in diamond. The group were able to amplify and detect the weak magnetic field noise (∼10 nT) from a single nuclear spin located ∼3 nm from the centre using dynamical decoupling control and achieve a detectable hyperfine coupling strength as weak as ∼300 Hz. They also confirmed the quantum nature of the coupling, and measured the spin-defect distance and the vector components of the nuclear field. The technique marks a step towards imaging, detecting and controlling nuclear spins in single molecules. 

 

(Jonathan Finley, 2013-11-22 09:07)
2013-11-20 20:16

Wallraff group demonstrate exchange interactions, superradiant states and subradiant states for two qubits placed two centimeters apart in an open one-dimensional space.

 

 

Figure 1: In a transmission line photons are forced to travel along the line connecting the two qubits, mediating interactions between the two. By tuning the qubit emission wavelength we tune the effective distance between two qubits.

The Wallraff group at ETH Zürich have demonstrated for the first time that strong interactions between two distant superconducting qubits in an open environment exist. When the two qubits are separated by multiples of λr/2, we observe the formation of super- and subradiant states. The subradiant state was found to have a lifetime more than 100 times as long as the lifetime of the superradiant state. For perspective, in initial experiments showing similar effects in ions, the subradiant state lived about 1.03 times as long as the superradiant state. Finding a two-qubit state in an open environment with a lifetime two orders of magnitude longer than a single qubit suggests that these systems could potentially be used as a quantum memory.

Furthermore, when the qubits are separated by odd multiples of λr/4, an exchange interaction between the qubits emerges which is mediated by the vacuum fluctuations of the 1D continuum at all frequencies. To our knowledge, our work presents the first observation of an exchange-type interaction mediated by photons over larger distances, i.e. the first instance of quantum systems interacting coherently at a distance, in a free space. We find good agreement of our experimental findings with the theory (Lalumiere et. al., Phys Rev A 88, 043806, 2013).


 
Figure 2: Interaction effects are revealed when measuring resonance fluorescence. An exchange splitting is seen at qubit separations of 3λr/4, while super- and subradiant states with drastically different lifetimes form for qubits separated by λr.

Full article:
http://www.sciencemag.org/content/early/2013/11/13/science.1244324.abstract

References: 
A. F. van Loo, A. Fedorov, K. Lalumière, B. C. Sanders, A. Blais, A. Wallraff, Science, 2013

 

(Jonathan Finley, 2013-11-20 20:16)
2013-11-20 20:09

SOLID partner Ronald Hanson is the 2012 recipient of the Nicholas Kurti European Science Prize.

 

Dr. Ronald Hanson from the Kavli Institute of Nanoscience, Delft University of Technology is the 2012 recipient of the Nicholas Kurti European Science Prize. This prize is intended to recognise and promote outstanding achievements of young scientists in the field of physical sciences research and to support their career development. Hanson receives a €8000 cash prize, a unique trophy and certificate. He also has the opportunity to present his work at a conference of his choice.

Hanson is a young investigator in the field of quantum nanoscience. His research is a search for stable qubits, the building blocks for a quantum computer. As a postdoc and FOM group leader, he became one of the pioneers of quantum science in diamond, a material in which quantum states are scarcely disrupted. Professor George Pickett of Lancaster University, chairman of the committee of senior scientists who assess the nominations, commented: "The work of Ronald Hanson on the behaviour of spins in quantum dots and diamond had very much impressed the committee, and we are happy to award him this year’s prize and wish him well in continuing the work in the future."

The Nicholas Kurti European Science Prize is named after Professor Nicholas Kurti, known for his distinguished work in ultra-low temperature physics at Oxford University. The prize is sponsored by Oxford Instruments, a provider of high technology tools and systems for research and industry. Previous winners of the prize include Prof.dr. Mathias Kläui, Dr. Christian Rüegg, Dr. John Morton, FOm workgroup leader Prof.dr. Lieven Vandersypen, former FOM PhD Sir Prof.dr. Kostantin Novoselov, Prof.dr. Andreas Wallraff and Dr. Silvano De Franceschi.

 

(Jonathan Finley, 2013-11-20 20:09)
2013-11-20 20:01

An ERC Advanced Grant was awarded to Andreas Wallraff by the European Research Council (ERC) for the project "Superconducting Quantum Networks".

 From 2014, Wallraff will be using the funds awarded to him by the Advanced Grant to investigate ways of developing networks for computers that operate on the basis of quantum physics: quantum computers. The technology is based on integrated electronic circuits that use superconductive materials, and in which information is processed at microwave frequencies. The project focuses on the development of networks that can connect individual quantum chips at distances ranging from a few centimeters to several meters. The scientist and his colleagues expect to be able to use these systems to solve complex problems and investigate the underlying properties of quantum physics.

 

(Jonathan Finley, 2013-11-20 20:01)
2013-11-20 19:49

Entangled diamonds...

The team led by R. Hanson at TU-Delft report in Nature (Bernien, H. et al. Nature http://dx.doi.org/10.1038/nature12016 (2013)) that they have entangled information kept in pieces of diamond 3 metres apart, so that measuring the state of one quantum bit (qubit) instantly fixes the state of the other - a step necessary for exchanging quantum information over large distances.

 
(Jonathan Finley, 2013-11-20 19:49)
2013-11-20 19:46

electrons transported between quantum dots...

Scientists from Delft University of Technology and the FOM Foundation have successfully allowed electrons to jump between quantum dots located far from each other. The electron jumped between the ends of a chain of three small semiconducting islands (so-called quantum dots) without crossing the island in the middle. This process makes it easier to use quantum dots in future quantum computers. The researchers published their findings on 28 April online in the journal Nature Nanotechnology.

 

Long-distance coherent coupling in a quantum dot array

Floris R. Braakman, Pierre Barthelemy, Christian Reichl, Werner Wegscheider, Lieven M. K. Vandersypen
Nature Nanotechnology, advance online publication (2013)

(Jonathan Finley, 2013-11-20 19:46)
2013-11-20 19:40

Two superconducting qubits entangled!

For more information, navigate to http://dicarlolab.tudelft.nl/entangling-quantum-circuits-by-measurement/ 

(Jonathan Finley, 2013-11-20 19:40)
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