Spontaneous Superradiance from Single Diamond Nanocrystals


Sarah Kaiser, Carlo Bradac, Mattias Johnsson, Matthew van Breugel, Ben Baragiola, Rochelle Martin, Mathieu L. Juan, Gavin Brennen, Thomas Volz

Department of Physics and Astronomy, Macquarie University

ARC Centre for Engineered Quantum Systems

Macquarie University logo EQuS logo

Motivation

Energy level diagram for NV centers

Cooperative behavior of NV in Nanodiamonds

Energy level diagram for NV centers
Centers must be indistinguishable
  1. spatial: $V << \lambda^3$
  2. spectral
  3. spin manifold

Modeling Cooperative Effects

How to describe cooperation?

Dicke States

$|J,M\rangle =\sqrt{\frac{(J+M)!(J-M)!}{(2J)!}}\sum_{perm}|\underbrace{111...}_{\text{J+M}}\underbrace{000...}_{\text{J-M}}\rangle$
$N$ # of two-level emitters
$J=\frac{N}{2}$ total spin for the collective system
$M\in\{-J,J\}$ projection of the spin state, J+M excited emitters


R H Dicke [doi:10/cbq3mc]

Example: Dicke States

$M,~N=3$
3/2 $|111\rangle$
1/2 $|110\rangle+|101\rangle+|011\rangle$
-1/2 $|100\rangle+|010\rangle+|001\rangle$
-3/2 $|000\rangle$

What degrades superradiance?

(Local) Distinguishability.

  • spin–spin coupling
  • local phononic environments
  • localized charge fields
  • lattice stress/strain
  • etc.

Distinguishable = Dephasing

Energy level diagram for NV centers

Superradiance model parameters

  1. Domain Size: max # of cooperating centers
  2. Initial state of system
  3. Bright/dark decay rates
  4. Local dephasing rates

C Bradac et al. [arXiv:1608.03119]

Observations

Decay rates for excitations

Energy level diagram for NV centers

Comparing rates to model:

Model fits for SR data

Initial state exploration

g2^{bar}(\tau) measurements

Extensions: Low temp

  1. # of cooperating centers : ✖
  2. Initial state of system : ➖
  3. Bright/dark decay rates : ?
  4. Local dephasing rates : ✔?
    B. B Prasanna Venkatesh, M L Juan,
    O Romero-Isart [arXiv:1705.07847]



Extensions: Low temp








Summary:

Seen:

  • Ultrafast radiative lifetimes $\approx1\text{ns}$
  • Photon correlations consistency check model

To Do:

  • Temperature dependance?
  • Other color centers?
  • Expand model: Dipole dipole interactions
  • Super absorption?

Aside: Research background

Long distance QKD optics payload Long distance QKD optics payload