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Quantum sources: Are diamonds your best friend?

By David Nugent


Enticed perhaps by successes with laboratory quantum key distribution demonstrations, academic and commercial interest in single photon sources (SPS) has accelerated in recent years. To celebrate the 50 year anniversary of the invention of the laser, I wrote an Innovation Brief on single photon sources and you can download a copy here.

Photo credit: Swamibu

Broadly speaking single-photon generators can be broken down into three categories:

  1. Nitrogen vacancies (‘NV’) in high-purity diamond.
  2. Single quantum dots (‘QDs’) encapsulated in nanostructures.
  3. Other methods such as spontaneous parametric downconversion.

CLEO/QELS 2010 does not disappoint with papers covering all three SPS topics, though admittedly the program is focused on NV and QD sources. Here is a selection of my own pick of the crop.

Quantum Emitter Photonic Devices

Monday, May 17, 3.45pm – 5.30pm

Presider: Won Park, Univ. of Colorado.

Stephan Reitzenstein (Univ. Wurzburg) et al will present work on high-efficient electrically driven quantum dot micropillar SPSs. The authors report a record high (34%) coupling efficiency and single photon emission rate of 35 MHz under pulsed electrical excitation. I will be interested to learn about the operating temperature of this configuration and the manufacturability of the micropillar structures.

Birgit Hausmann (Harvard Univ.) et al will present work on a hybrid diamond-plasmon particle device containing individual NV centers for QIP and quantum cryptography applications. My personal view is that plasmon enhancement could play a crucial role in the realisation of practical single-photon sources, so this talk is particularly interesting for me.

Finally, Matthew Rakher (NIST) et al will discuss progress on fiber-coupled waveguides for enhanced resonant interactions with single QD sources. I wonder method of fiber coupling Rakher will present. Photonic crystal fibers, I guess?

QELS Symposium on Quantum Repeaters and Networks (QWD)

Wednesday, May 19, 1.30pm to 3.15pm

Presider: Christoph Simon (Univ. of Calgary)

Continuing the theme started by Rakher et al the day before, Paul Barclay (Hewlett Packard) et al will present work on optical coupling between NV centers in single-crystal diamond and hybrid gallium phosphide microcavities.

Poster Session

Wednesday, May 19

Although I have read many papers on the embedding of NV centers into nanostructures to achieve Purcell effect efficiency enhancements, I have never heard about embedding a single-photon crystal source inside or atop a host crystal. A poster by Luke Stewart (Macquarie Univ.) et al show how the lifetime of NV emitters can be increased by incorporating nano-diamonds inside opals and the lifetime variance may be reduced by placing them on the surface of opals.

Australia boasts some great credentials in the development and exploitation of SPS science and applications, including the renown R&D labs at Quantum Communications Victoria. Will anyone from QCV will be attending CLEO/QELS this year? It would be great to hook up with them.

QELS: Single Emitters and Photons

Thursday, May 20, 4:45 p.m.–6:30 p.m.

Presider: Charles Santori (Hewlett-Packard Labs)

This session contains two papers discussing the post-production treatment of diamond-embedded NV centers. Santori himself will present a method for converting neutral NV centers to the desired negatively charged state, while Russell Barbour (Univ. of Oregon) will discuss the role of deformed silica microspheres in enhancing evanescent coupling between whispering gallery modes and neighboring NV centres embedded in diamond nanopillars.

What are your views on NV versus QD single photon sources? What are the biggest hurdles confronting each method? Drop us a note. Let’s debate!

Dr David Nugent is Founder and CEO of Elucidare Limited, a boutique technology development and investment advisory business.

Posted: 5 May 2010 by David Nugent | with 0 comments

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