Coherent excitation of Rydberg atoms on an atom chip

Coherent excitation of Rydberg atoms on an atom chip

Rutger M. T. ThijssenVan der Waals - Zeeman Instituut voor

Experimentele Natuurkunde

Quantum Information Processing Qubits Coherence Switchable interactions Scalability

MAGCHIPS

MAGCHIPS Permanent magnetic lattice atom chip Gold-coated for laser cooling 500 populated magnetic microtraps

Prospective qubits 87Rb, T~mK

10 µm22 µm

Magnetised film

“Atom chip”(room temperature)

Neutral atoms: intrinsically weak interaction with environment Exquisite control & manipulation Scalability Stable qubits

Quantum information on MAGCHIPS

Neutral atoms: intrinsically weak interaction with environment Exquisite control & manipulation Scalability Stable qubits

Quantum information on MAGCHIPS

Intrinsically weak interaction with environment Good: long coherence times (~sec.) Challenge: quantum information requires interaction: we have to

work to add an interaction between qubits (i.e. traps)

Rydberg atoms Hydrogen-like atom High principal (n) quantum

number Large dipole-dipole interaction

between Rydberg atoms

Dipole blockade

32121 )ˆ)(ˆ(3

RRRV

mmmm

2nm

Rydberg Excitation

Toptica DL-100 diode laser (30mW)

Toptica TA-SHG 110 frequency doubled diode laser, tunable from 488-479nm (n=18-ionization threshold) (300mW)

|nd

|5s

|5p

780nm (infrared)

480nm (blue)

|ns

Electromagnetically Induced Transparency

|nd

Ec

ji ,m

ppc

pp i

L

12

22 244)(

|5s

|5p

Ωp

δωp

γ12

Detuning (δωp)

Electromagnetically Induced Transparency

|nd

Ec

ji ,m

ppc

pp i

L

12

22 244)(

|5s

|5p

Ωc

Ωp

δωp

γ12

Detuning (δωp)

Electromagnetically Induced Transparency – dressed states

|a+

780nm (infrared)

|a0 (5s)

|a-

Rediagonalise interaction Hamiltonian

Interference between |a+ and |a- dressed states: reduced probe absorption on two-photon resonance

|5s

|5p

|nd

Ωc

Ωp

Autler – Townes splitting + Fano interference

EIT – frequency stabilisation in a vapour cell

Coupling laser detuning (MHz)

vapour cell EIT, |39ddichroic mirror

dichroic mirror

Rubidium vapour cell

fast photodiode

780 nm diode laser

480 nm diode laser

EIT Imaging

optical fiber

EIT Imaging

optical fiber

Position (px)

Detu

ning

(MHz

)O

ptica

l den

sity

EIT Imaging Blue laser frequency locked to vapour cell EIT Red laser scanned over resonance

Surface effects• Near-field blackbody radiation from chip • “mirror” effect: Rydberg atom interacting with itself• Photoelectric effect on surface: adsorbed Rb, Au• Patch potentials

• Crystal defects in FePt• Adsorbed Rb ions

eV58.2/ hcE

Summary MAGCHIPS experiment Rydberg / EIT for interactions between qubits

Built laser system Built frequency locking setup for probe and coupling laser

Imaged Rydberg / EIT in surface magneto-optical trap

Investigating effects of surface on Rydberg levels Build a quantum computer…

Summary MAGCHIPS experiment Rydberg / EIT for interactions between qubits

Built laser system Built frequency locking setup for probe and coupling laser

Imaged Rydberg / EIT in surface magneto-optical trap

Investigating effects of surface on Rydberg levels Build a quantum computer…

THANK YOU Questions?

Rutger M. T. [email protected]

2-photon gates Zoller Mesoscopic Rydberg gates using EIT

Rydberg interaction

|0> |1>

|0> |1>

Focused lasers

Ensemble A Ensemble B

Microwave/Raman6.8 GHz

Rydberg Atoms One highly excited

electron (n=20-100) Rydberg formula: Size ~ n^2 Lifetime ~ n^3 Polarisability ~n^7 Van der Waals

interaction ~ n^11 Dipole blockade shifts

nearby Rydberg levels

32121 )ˆ)(ˆ(3

RRRV

mmmm

2nm

2)( l

HB n

hcRE