Jason HoganJuly 24, 2018

Undergraduate Summer Research

Seminar

Precision atom interferometry for

fundamental physics

Atom interference

Light interferometer

Atom interferometer

Atom

http://scienceblogs.com/principles/2013/10/22/quantum-erasure/

http://www.cobolt.se/interferometry.html

Light fringes

Beam

splitte

r

Beam

splitte

r

Mirro

r

Atom fringes

Light

Atom optics using light

ħkv = ħk/m

ħk

(1) Light absorption:

(2) Stimulated emission:

Atom optics using light

ħkv = ħk/m

ħk

(1) Light absorption:

(2) Stimulated emission:

Rabi oscillations

Time

In practice, typically 2-photon Raman or Bragg transitions

Atom

Beam

splitte

r

Beam

splitte

r

Mirro

r

Light Pulse Atom Interferometry

p/2 pulse “beamsplitter”

p pulse “mirror”

“beamsplitter”p/2 pulse

•Interior view |p+k>

|p >

Time

Posi

tion

Light Pulse Atom Interferometry

• Long duration

• Large wavepacket separation

10 meter scale atomic fountain

Interference at long interrogation time

Wavepacket separation at apex (this data 50 nK)

Dickerson, et al., PRL 111, 083001 (2013).

Interference (3 nK cloud)

Port 1

Port 2

2T = 2.3 seconds

1.4 cm wavepacket separation

54 cm

Large space-time area atom interferometry

Long duration (2 seconds), large separation (>0.5 meter) matter wave interferometer

Kovachy et al., Nature 2015

90 photons worth of momentum

max wavepacketseparation

World record wavepacket separation due to multiple laser pulses of momentum

Large space-time area atom interferometry

2 ħk

90 ħk

Robust interference observed at macroscopic time and length scales

Kovachy et al., Nature 2015

Phase shift from spacetime curvature

Spacetime curvature across a single particle's wavefunction

General relativity: gravity = curvature (tidal forces)

Curvature-induced phase shifts have been described as first true manifestation of gravitation in a quantum system

Gravity Gradiometer

Gradiometer interference fringes

10 ћk 30 ћk

Gradiometer baseline defined by atom recoil:

(Insensitive to initial source position)

P. Asenbaum et al., PRL 2017.

Phase shift from tidal force

Gradiometer response to 84 kg lead test mass

Asenbaum et al., PRL 118, 183602 (2017)

Upper interferometer

Lower interferometer

Equivalence Principle

Bodies fall at the same rate, independent of composition

Why test the EP?

▪ Foundation of General Relativity

▪ Quantum theory of gravity (?)

▪ Search for new forces, dark matter

C. Will, Living Reviews

mg = ma

EP Bounds from Classical Experiments

𝜂 𝑀, 𝐸 = −1.0 ± 1.4 × 10−13

Williams et al, PRL 2004

©news.cnrs.fr

Lunar laser ranging:

Torsion pendula: 𝜂 𝐵𝑒, 𝑇𝑖 = 0.3 ± 1.8 × 10−13

Schlamminger et al, PRL 2008

©npl.Washington.edu

MICROSCOPE satellite: 𝜂 𝑇𝑖, 𝑃𝑡 = −0.1 ± 1.3 × 10−14

Touboul et al, PRL 2017

©CNES, D. Ducros

Phase shear readout

Measure phase + contrast in one shot

(Sugarbaker et al, PRL 2013)

Suppresses time varying effects (mirror motion, laser phase, etc.)

Bragg Interferometer

• Common Bragg laser beams

• Common velocity selection

• AC stark shift compensation

Simultaneous dual species interferometers

10ħk Dual Species Run

Rb-85

Rb-87

Rb-85 and Rb-87

are in phase

2T = 1.8 s

Megaparsecs…

Gravitational waves science:

• New carrier for astronomy: Generated by moving mass instead of electric charge

• Tests of gravity: Extreme systems (e.g., black hole binaries) test general relativity

• Cosmology: Can see to the earliest times in the universe

L (1 + h sin(ωt ))

strain

frequency

Gravitational Wave Detection

Laser Interferometer Detectors

Gound-based detectors: LIGO, VIRGO, GEO (> 10 Hz)

Space-based detector concept: LISA

(1 mHz – 100 mHz)

Gravitational wave frequency bands

Mid-band

There is a gap between the LIGO and LISA detectors (0.1 Hz – 10 Hz).

Moore et al., CQG 32, 015014 (2014)

Mid-band Science

Mid-band discovery potential

Historically every new band/modality has led to discovery

Observe LIGO sources when they are younger

Optimal for sky localization

Predict when and where events will occur (before they reach LIGO band)

Observe run-up to coalescence using electromagnetic telescopes

Astrophysics and Cosmology

Black hole, neutron star, and white dwarf binaries

Ultralight scalar dark matter discovery potential

Early universe stochastic sources? (cosmic GW background)

Sky position determination

λ

Sky localization precision:

Mid-band advantages

- Small wavelength λ

- Long source lifetime (~months) maximizes effective R

Images: R. Hurt/Caltech-JPL; 2007 Thomson Higher Education

R

Measurement Concept

Essential Features

1. Light propagates across the baseline at a constant speed

2. Atoms are good clocks

Atom

Clock

Atom

Clock

L (1 + h sin(ωt ))

Simple Example: Two Atomic Clocks

Time

Phase evolved by atom after time T

Atom clock

Atom clock

Simple Example: Two Atomic Clocks

GW changes light travel time

Time

Atom clock

Atom clock

Gradiometer sensor design

• Compare two (or more) atom ensembles separated by a large baseline

• Science signal is differential phasebetween interferometers

• Differential measurement suppresses many sources of common noise and systematic errorsM

easu

rem

ent

Base

line g

Science signal strength is proportional to baseline length (DM, GWs).

Clock Gradiometer

atoms

atoms

Projected gravitational wave sensitivity

Dots indicate remaining lifetimes of 10 years, 1 year, 0.1 years, and 0.01 years

MAGIS-100 detector at Fermilab

• MINOS, MINERνA, NOνA experiments use NuMI beam

• 100 meter access shaft – 100 meter atom interferometer

• Search for dark matter coupling in the Hz range

• Intermediate step to full-scale detector for GWs

Source 1

Source 2

50 m

ete

rs50 m

ete

rs

100 m

ete

rs

Source 3

Matter wave Atomic Gradiometer Interferometric Sensor

Stanford MAGIS prototype

Atom optics laser

(M Squared SolsTiS)

Trapped Sr atom cloud

(Blue MOT)

Sr gradiometer CAD

(atom source detail)

Two assembled Sr atom sources

Collaborators

Rb Atom InterferometryMark Kasevich

Tim Kovachy

Chris Overstreet

Peter Asenbaum

Remy Notermans

Theory:Peter Graham

Savas Dimopoulos

Surjeet Rajendran

Asimina Arvanitaki

Ken Van Tilburg

MAGIS-100:

Joseph Lykken (Fermilab)

Robert Plunkett (Fermilab)

Swapan Chattopadhyay (Fermilab/NIU)

Jeremiah Mitchell (Fermilab)

Roni Harnik (Fermilab)

Phil Adamson (Fermilab)

Steve Geer (Fermilab)

Jonathon Coleman (Liverpool)

Sr Atom InterferometryTJ Wilkason

Hunter Swan

Jan Rudolph

Yijun Jiang

Ben Garber

Benjamin Spar

Connor Holland