Quantum Optics and Atomic Physics

NBI PhD afternoon 2016

Karsten Dideriksen

QUANTOP

Precision Measurements with Atoms and Molecules

– Current projects

Cavity QED for atomic clocks:

Spectrally ultra-narrow laser

sources

Aims and objectives:

Collective physics in cavities

Generating ultra-narrow laser

Superradiant laser sources

Compact molecular clocks

Strontium-88

Molecules

Precision Measurements with Atoms and Molecules

– Recent results

B. T. R. Christensen et al., PRA 92, 053820 (2015)

Atomic phase-response

signal for laser locking

Collectively enhanced atomic

emission

Theoretical Quantum Optics

Theoretical Quantum Optics

Quantum Information in practice

• Atoms

• Ions

• Superconducting qubits

• Cavities

• Quantum dots

• Photons

• All work is in close collaboration with experimental groupsaround the world

Any system that we think will work

Come join the QuantumInformation course

in block 4

Quantum Photonics

Quantum Dots – Solid State Artificial Atoms

Lodahl, Mahmoodian & Stobbe, Interfacing single photons and single quantum dots with photonic nanostructuresRev. Mod. Phys. 87, 347 (2015).

Quantum dots in photonic nanostructures: a platform for all-solid-state quantum optics

hole

electron

Excitons for single-photon emission

Single electron (or hole) as optically adressable

Building Blocks for Integrated Quantum

Photonic Circuits

Single-photon source and nonlinearity

Efficient coupling to dielectric waveguides for long-range propagation

Photon circuits based on dielectric waveguides

On-chip single-photon detectors based on superconducting nanowires

Lodahl, Mahmoodian & Stobbe, Interfacing single photons and single quantum dots with photonic nanostructuresRev. Mod. Phys. 87, 347 (2015).

QUANTOP

QUANTOP

Semiconductor

• Opto-mechanics (membrane)

Atoms

• Nanofibre

• Glass cell

Hybrid (membrane + atoms)

QUANTOP

Quantum Membranes

• Only 100 nm thick• Few mK• Single phonon level• Light Squeezing

QUANTOP

Nanofibre

Quantum State Engineering

Quantum Metrology

Quantum Information

QUANTOP

Caesium vapour cells

• An ensemble of longlived spins

Applications

• Biomagnetometry

• Quantum Information:– Entanglement

– Teleportation

– Single photon source

mF = 4

mF = 3

Zeeman

splitting1b

mF = 2

Positivefrequencyoscillator

Negativefrequencyoscillator

𝑋 𝑡 − 𝑋0 𝑡 = 𝑋 0 −𝑋0 0 ]cos 𝜔𝑡 + [𝑃 0 + 𝑃0 0 sin 𝜔𝑡

Entanglement of an oscillator with an atomic spin

J

Synchronizedto better than

Standard QuantumLimit

4/1)()( PVarXVar * * <

On-demand single photon source

Motivation• Various applications in quantum information

(e.g. cryptography, quantum simulators)• Focus: Quantum repeater

≠

Read

4

3

3'

4'

5'

F

3 4 5mF

9.2 GHz|1>

|0>

~1 GHz

Single Photon

On-demand single photon source

4

3

3'

4'

5'

F

3 4 5mF

Write

9.2 GHz|1>

|0>

~1 GHz

heralding

Single Photon

|𝜓 ∝

𝑗=1

𝑁

𝑐𝑗𝑒𝑖∆𝒌∙𝒓 |𝑔1𝑔2…𝑠𝑗 … 𝑔𝑁

[1]

[1] Heng Shen, PhD Thesis, University of Copenhagen, 2015

Quantum Optics and Atomic Physics