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Single-Photon Metrology & Technology

We are working on single photon technology including detectors, sources, processing. We are also developing both metrology of those devices as well as metrology methods making use of single-photon technology.

- Our detector efforts include

a) the testing of IR photon counting APDs prototypes under development by a number of groups. One goal of this effort is to encourage the development of high-efficiency (> 60%) and low-dark-count (%lt;1000 Hz) photon counting detectors for the 1 µm to 1.6 µm spectral region. Trade-offs between detection efficiency and dark counts can be seen in Figure 1.

Detector test apparatus

Figure 1a. Detector test apparatus.
 Figure 1

Figure 1b. Prototype detector test results.
b) the development of an infrared high-efficiency near-zero-dark-count detector with photon-number resolving capability. This is a collaboration led by Sae Woo Nam of NIST, Boulder. Sae Woo and his detector can be seen in Figure 2.
Sae Woo and his detector

Figure 2. Sae Woo and his detector.
detector

The detector


c) the development of a detector system using a deadtime management scheme (Figure 3) that is capable of operating at higher detection rates while maintaining low deadtime fractions. This is a collaboration with Michael Ware of BYU and the team of Ivo DeGiavanni of INRIM, Turin, Italy.

  • Use pool of detectors as a resource to register high rate of incoming photons
  • Incoming photon switched to any ready detector
  • If it fires detector is switched out of ready pool until recovery
  • If it does not fire detector remains ready
  • Allows operation at higher than single detector rates
  • Allows operation near "100% dead" rate
  • Max rate limited by detection efficiency and number of detectors.
Figure 3
Figure 3. ~30 ns deadtime, but only after firing 0 ns deadtime after not firing.

- Our source efforts include

  • the development of a compact robust way of producing a Polarization Entangled Photon pair Source for quantum cryptography. This effort is a wide collaboration to produce photons for both free-space and fiber-based cryptography links (Figure 4).
Source prototyping,
Engineering, and Characterization		 Warren Grice, Oak Ridge Nat'l Lab.
Alan Migdall, NIST
Franco Wong, MIT
Pump source Prem Kumar, Northwestern Univ.
Franco Wong, MIT
Crystal development David Zelmon, Wright-Patterson AFB
Fiber-based pair source Alan Migdall, NIST
Fiber coupling and entanglement John Howell, Univ. of Rochester
Tom Bahder, Army Research Lab
Miniaturization Ray Beausoleil, Hewlett Packard

Figure 4. Polarization Entangled Photon Pair Source Integration Team.
     There are two approaches:
  • One visible source for a free space optical link (figure 5).
  • One IR source for fiber telecom link. We have a program to develop two-photon sources based on chi(3) nonlinearity in a microstructure fiber. This nonlinearity takes two pump photons and creates a correlated pair. It can be arranged that two degenerate pump photons can be converted to one redder and one bluer photon or the backward process can be arranged where a red and blue photon are converted in to correlated pair at the center frequency. The conversion efficiency of this nonlinear process is enhanced in a microstructure fiber because the small fiber core size allowing low pump powers and making possible compact sources.
 Figure 5
Figure 5. Robust Compact Fieldable Entangled Photon Source Collaboration.
Schematic

Figure 6. Two degenerate photons in, two non-degenerate photons out.		 Figure 7

Figure 7. Microstructure fiber (MF) output spectrum.
  • The development of a single-photon source using a multiplexed array of parametric down-converters. This is an approach to solve the problem of producing single photons in a truly on-demand fashion for use in quantum communication. Ultimately what is needed is a train of single photons for use in quantum circuits operating the way a clock pulse train does in electronic circuits. Currently "single photon" sources cannot produce single photons with high probability, without also having a high probability of producing more than one photon. Producing more than one photon at a time can compromise quantum cryptographic schemes. Using multiplexed arrays of single photon sources and optical switching, it will be possible to independently control the probability to produce a single photon and more than one photon. (Fig. 8).
Figure 8a

Figure 8a. Entangled photons via Parametric Down Conversion (PDC) 		Figure 8b
Figure 8b.

- Our metrology efforts include

  • the development of accurate methods to measure photon-counting detection efficiency. One scheme uses the parametric down-conversion, which produces two photons at a time so that when one is detected we know when and where the other photon will arrive. This type of source is particularly useful in the calibration of detector efficiency. We have tested the accuracy limits of this method by comparison to conventional measurement methods with an uncertainty of better than 0.2%. (Fig 9). For more information see Correlated Photon Radiometry.
 Primary standard detector calibration method

Figure 9. Primary standard detector calibration method.
  • A new program we call Quantum Optical Metrology with N-Photons: optical measurements that rely on the quantum-engineered states of light to obtain higher precision than can be obtained using classical states of light. Combining the resources of Richard Mirin, Sae Woo Nam, Marty Stevens, of EEEL; Manny Knill and Scott Glancy of ITL; and Alan Migdall of PL.
    •
States of Light Status States of Light
Laser pump sources and optical switching systems are being evaluated for implementing method.

Our efforts on sources include the development of compact robust entangled photon sources for quantum cryptography. We have formed a team. NIST is part of a DTO funded multi-team effort to build a compact robust entangled photon source for use in Quantum Cryptography. Efforts are underway to develop one source of visible photons using parametric downconversion for a free-space space cryptography link and another source of infrared photons using microstructure fiber for a fiber telecom cryptography link.

Quantum Optical Metrology with N-Photons: optical measurements that rely on the quantum-engineered states of light to obtain higher precision than can be obtained using classical states of light.
Pre 1960 light  
  Photo of scientists in the laboratory
Laser invented		  
  2005 to 2010?
The movement to more controlled and engineered states of light opens the possibility for significant advances in measurement capability.

Quantum States of Light

Examples of engineered states of light include:
  • Photon Number (fock) state: Fock State, N, contains exactly N photons

  • Entangled state: A multiparticle state whose wavefunction cannot be written as a product state; the particles are "extremely linked."
On-demand, Entangled photon pairs can be made using
  1. Parametric down conversion or by

  2. Combining indistinguishable single photons
High "NOON" states, which are path-entangled states with N-photons and are written as

$|N::0\rangle = ( |N,0\rangle + |0,N\rangle ) \quad |N::0\rangle = \exp (-iN\omega t) |N::0 (0)\rangle$

offer much measurement potential because an N-photon state evolves N times faster than single photon states!

Examples of Quantum Optical Metrology

Such states may be of use for applications such as precision length measurements:
  • photolithography
  • navigation (optical gyros)
  • astrophysics
  • gravity waves
as well as less traditional applications like
  • Nanotechnology
    • Super-resolving optical microscopy
    • Quantum lithography
  • Biotech
    • Non-invasive imaging
    • Enhanced N-photon microscopy
    • Quantum Optical Coherence Tomography
We will use our expertise with quantum dots with two photon states photon number revolving dots and the theory of linear optical Quantum Computing to make there large number of entangled photon states.

Single photons on-demand via quantum dots (Mirin)

Figure 10. Single photons on-demand via quantum dots (Mirin).		 Figure 11

Figure 11. Qdot correlation map. Missing peak indicates single pulses do not contain multiple photons.

- Our goals are to

  • Demonstrate bright N-photon entangled quantum states of light, N > 5 (Goal is N = 10 or more)

  • Understand the limitations of quantum state tomography (QST) and quantify uncertainties

  • Perform quantum optical metrology, including Heisenberg-limited interferometry, using N-photon states

  • Construct a quantum optical metrology testbed with all of the necessary tools (Quantum state generators and measurement schemes) for demonstrating new theoretical proposals

  • Advance quantum state engineering and photon metrology
For technical information or questions, contact:

Alan Migdall
Phone: (301) 975-2331
Fax: (301) 869-5700
Email: amigdall@nist.gov

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Online: March 2007