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Enhancing the quantum sensing capabilities of diamond: Shooting electrons at diamonds can introduce quantum sensors into them


Researchers have discovered that dense ensembles of quantum spins can be created in diamond with high resolution using an electron microscopes, paving the way for enhanced sensors and resources for quantum technologies.

Diamonds are made of carbon atoms in a crystalline structure, but if a carbon atom is replaced with another type of atom, this will result in a lattice defect. One such defect is the Nitrogen-Vacancy (NV), where one carbon atom is replaced by a nitrogen atom, and its neighbor is missing (an empty space remains in its place).

If this defect is illuminated with a green laser, in response it will emit red light (fluoresce) with an interesting feature: its intensity varies depending on the magnetic properties in the environment. This unique feature makes the NV center particularly useful for measuring magnetic fields, magnetic imaging (MRI), and quantum computing and information.

In order to produce optimal magnetic detectors, the density of these defects should be increased without increasing environmental noise and damaging the diamond properties.

Now, scientists from the research group of Nir Bar-Gill at the Hebrew University of Jerusalem’s Racah Institute of Physics and Department of Applied Physics, in cooperation with Prof. Eyal Buks of the Technion – Israel Institute of Technology, have shown that ultra-high densities of NV centers can be obtained by a simple process of using electron beams to kick carbon atoms out of the lattice.

This work, published in the scientific journal Applied Physics Letters, is a continuation of previous work in the field, and demonstrates an improvement in the densities of NV centers in a variety of diamond types. The irradiation is performed using an electron beam microscope (Transmission Electron Microscope or TEM), which has been specifically converted for this purpose. The availability of this device in nanotechnology centers in many universities in Israel and around the world enables this process with high spatial accuracy, quickly and simply.

The enhanced densities of the NV color centers obtained, while maintaining their unique quantum properties, foreshadow future improvements in the sensitivity of diamond magnetic measurements, as well as promising directions in the study of solid state physics and quantum information theory.

Nitrogen Vacancy (NV) color centers exhibit remarkable and unique properties, including long coherence times at room temperature (~ ms), optical initialization and readout, and coherent microwave control.

“This work is an important stepping stone toward utilizing NV centers in diamond as resources for quantum technologies, such as enhanced sensing, quantum simulation and potentially quantum information processing”, said Bar-Gill, an Assistant Professor in the Dept. of Applied Physics and Racah Institute of Physics at the Hebrew University, where he founded the Quantum Information, Simulation and Sensing lab.

"What is special about our approach is that it's very simple and straightforward," said Hebrew University researcher Dima Farfurnik. "You get sufficiently high NV concentrations that are appropriate for many applications with a simple procedure that can be done in-house."

CITATION: Farfurnik, D., et al. Enhanced concentrations of nitrogen-vacancy centers in diamond through TEM irradiationAppl. Phys. Lett. 111, 123101 (2017). Publisher's Version

SUPPORT: This work was supported in part by the Minerva ARCHES award, the CIFAR-Azrieli global scholars program, the Israel Science Foundation (Grant No. 750/14), the Ministry of Science and Technology, Israel, the Technion security research foundation, and the CAMBR fellowship for Nanoscience and Nanotechnology.

PHOTO 1: http://media.huji.ac.il/new/photos/hu171114_bar-gill.jpg - Diamond sample illuminated by green light in our home-built microscope. Sample is placed on a special mount, within a printed circuit board, used to deliver microwaves which allow quantum manipulations and magnetic sensing with the NVs. (Credit: Yoav Romach)

PHOTO 2: http://media.huji.ac.il/new/photos/hu171114_bar-gill-cryo.jpg - Cryogenic sample chamber, with diamond sample mounted on copper cold plate. (Credit: Yoav Romach)

PHOTO 3: https://drive.google.com/file/d/1TsGTAKrw1l_dw2X2tUDlbBluwnP_LoGf/view - Hebrew University researchers Nir Bar-Gill and Dima Farfurnik with a diamond magnetic microscope. (Credit: Nir Bar-Gill)

Enhancing the quantum sensing capabilities of diamond: Shooting electrons at diamonds can introduce quantum sensors into them

Hebrew University’s Quantum Information Science Center wins tender to build national quantum communications system


Research at Israel’s leading quantum science center paves the way for massive improvements in computation speed and secure communication

The Quantum Information Science Center at the Hebrew University of Jerusalem has won a NIS 7.5 million tender from the Government of Israel to lead the construction of a national demonstrator for quantum communications technologies. 

The goal of this project is to develop homegrown Israeli expertise and technology for a national quantum communications system that will prevent eavesdropping, protect data privacy and secure national infrastructure.

Prof. Nadav Katz, director of the Quantum Information Science Center, and a researcher at the Hebrew University’s Racah Institute of Physics, said: "This project to build a national quantum communications system will position Israel in the leading edge of research toward ultimately secured communication systems. With support from the Government of Israel and in cooperation with our research partners, this is the first Israeli national project in the emerging field of quantum information technologies.”

Quantum information research is one of the hottest areas in 21st century science, promising dramatic improvements in computation speed and secure communication. Based on the inherent wave-like nature of matter and light, it will lead to massive leaps forward in our ability to fabricate, control, measure and understand advanced structures.

To help drive this field forward, in 2013 the Hebrew University founded the Quantum Information Science Center (QISC) and recruited an interdisciplinary team of over 20 researchers from physics, computer science, mathematics, chemistry, philosophy and engineering. Representing the vanguard of Israel’s quantum researchers, this group is advancing our understanding of quantum information science and the development of quantum technologies.

As part of this project, researchers will build a communication system at the Hebrew University’s laboratories based on single photons representing quantum bits. Quantum bits make it possible to perform calculations in new ways that are not possible in current communications systems or even supercomputers.

Current methods of encrypting data are increasingly vulnerable to attack as the increased power of quantum computing comes online. Quantum communication systems use the laws of physics to secure data and are therefore resistant to attack.

Commercial quantum communication systems are not subject to peer review by Israeli experts and are therefore not suitable to the needs at hand. An Israeli implementation, subject to peer review and hack testing by Israeli scientists, is an essential national resource.    

The NIS 7.5 million contract was awarded by the Ministry of Defense, which is tasked with developing a secure communications infrastructure to improve privacy and secure national infrastructure. Also participating in the project are Rafael Advanced Defense Systems Ltd. and Opsys technologies, and an additional researcher from Tel Aviv University.

About the Quantum Information Science Center:

The Quantum Information Science Center (QISC) of the Hebrew University is a unique center for investigating both fundamental and applied science of quantum information. Its mission is to understand how quantum systems can be controlled and isolated to reach goals of communication, sensing, simulation and computation beyond the state of the art of any classical system. Bringing together diverse disciplines and methodologies, the Center has revolutionized many aspects of the field, including quantum computing threshold and security theorems, quantum control and thermodynamics, and many exciting experimental implementations such as optical, diamond vacancies, superconducting and more. For more information, please visit http://qcent.huji.ac.il/

- Dov Smith

Hebrew University’s Quantum Information Science Center wins tender to build national quantum communications system

Quantum Leap: Scientists Demonstrate a Compact, Efficient Single Photon Source That Can Operate at Ambient Temperatures On a Chip


Highly directional single photon source concept is expected to lead to a significant progress in producing compact, cheap, and efficient sources of quantum information bits for future applications

Quantum information science and technology has emerged as a new paradigm for dramatically faster computation and secure communication in the 21st century. At the heart of any quantum system is the most basic building block, the quantum bit or qbit, which carries the quantum information that can be transferred and processed (this is the quantum analogue of the bit used in current information systems). The most promising carrier qbit for ultimately fast, long distance quantum information transfer is the photon, the quantum unit of light.

The challenge facing scientists is to produce artificial sources of photons for various quantum information tasks. One of the biggest challenges is the development of efficient, scalable photon sources that can be mounted on a chip and operate at room temperature. Most sources used in labs today have to be very cold (at the temperature of liquid Helium, about -270C), which requires large and expensive refrigerators. Many sources also emit photons in undefined directions, making efficient collection a hard problem.

Now, a team of scientists from the Hebrew University of Jerusalem has demonstrated an efficient and compact single photon source that can operate on a chip at ambient temperatures. Using tiny nanocrystals made of semiconducting materials, the scientists developed a method in which a single nanocrystal can be accurately positioned on top of a specially designed and carefully fabricated nano-antenna.

In the same way large antennas on rooftops direct emission of classical radio waves for cellular and satellite transmissions, the nano-antenna efficiently directed the single photons emitted from the nanocrystals into a well-defined direction in space. This combined nanocrystals-nanoantenna device was able to produce a highly directional stream of single photons all flying to the same direction with a record low divergence angle. These photons were then collected with a very simple optical setup, and sent to be detected and analyzed using single photon detectors.

The team demonstrated that this hybrid device enhances the collection efficiency of single photons by more than a factor of 10 compared to a single nanocrystal without the antenna, without the need for complex and bulky optical collection systems used in many other experiments. Experimental results show that almost 40% of the photons are easily collected with a very simple optical apparatus, and over 20% of the photons are emitted into a very low numerical aperture, a 20-fold improvement over a freestanding quantum dot, and with a probability of more than 70% for a single photon emission. The single photon purity is limited only by emission from the metal, an obstacle that can be bypassed with careful design and fabrication.

The antennas were fabricated using simple metallic and dielectric layers using methods that are compatible with current industrial fabrication technologies, and many such devices can be fabricated densely on one small chip. The team is now working on a new generation of improved devices that will allow deterministic production of single photons straight from the chip into optical fibers, without any additional optical components, with a near unity efficiency. 

"This research paves a promising route for a high purity, high efficiency, on-chip single photon source operating at room temperature, a concept that can be extended to many types of quantum emitters. A highly directional single photon source could lead to a significant progress in producing compact, cheap, and efficient sources of quantum information bits for future quantum technological applications", said Prof. Ronen Rapaport, of the Racah Institute of Physics, The Department of Applied Physics, and the Center of Nanoscience and Nanotechnology at the Hebrew University of Jerusalem.

The Hebrew University of Jerusalem is Israel’s leading academic and research institution, producing one-third of all civilian research in Israel. For more information, visit http://new.huji.ac.il/en.

FUNDING: The research was supported in parts by the Einstein Foundation Berlin; the U.S. Department of Energy: Office of Basic Energy Sciences, Division of Materials Sciences and Engineering; the European Cooperation in Science and Technology through COST Action MP1302 Nanospectroscopy;  and by the Ministry of Science and Technology, Israel.

REFERENCE: Highly Directional Room-Temperature Single Photon Device. Nitzan LivnehMoshe G. HaratsDaniel IstratiHagai S. Eisenberg, and Ronen Rapaport. Nano Lett., 2016, 16 (4), pp 2527–2532. DOI: 10.1021/acs.nanolett.6b00082. Link: http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.6b00082

Quantum Leap: Scientists Demonstrate a Compact, Efficient Single Photon Source That Can Operate at Ambient Temperatures On a Chip
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