Quantum Computing with Atoms Christopher Monroe Computing and Information

Alan Turing (1912-1954) universal computing machines

moving CPU

011 Claude Shannon (1916-2001) quantify information: the bit read/write device

1 0 1 1 0 0 1 푘

memory tape 퐻 = − ෍ 푝푖푙표푔2푝푖 푖=1 vacuum tubes ENIAC (1946)

МЭСМ (1949) solid-state transistor Colossus (1943) (1947) Moore’s Law exponential growth in computing

Transistor density relative to 1978 Richard 100,000 Feynman 10,000

1,000

100 There's Plenty of Room at the Bottom (1959)

10 “When we get to the very, very small world – say circuits of seven atoms – we have a lot of new things that would happen 1 that represent completely new opportunities for design. Atoms 1980 1990 2000 2010 2018 on a small scale behave like nothing on a large scale, for they satisfy the laws of quantum mechanics…” Quantum Information Science

|0|0 state Entanglement OR

superposition |1|1 state a|0|0 + b|1|1

entanglement: “wiring without wires” Good News… …Bad News… …Good News! parallel processing measurement gives quantum interference on 2N inputs random result e.g., N=3 qubits

f(x) f(x)

a |000 + a |001 + a |010 + a |011 depends 0 1 2 3 on all inputs a4 |100 + a5|101 + a6 |110 + a7 |111

N=300 qubits have more configurations than there are David Deutsch particles in the universe! (early 1990s) Application: Factoring Numbers

A quantum computer can factor numbers exponentially faster than classical computers P. Shor (1994) 39 = 3  13 (…easy) 38647884621009387621432325631 = ?  ?

quantum wavefunction 휓(푛)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 Application: Optimization Molecular Simulations • designer materials • new catalysts • protein folding

Traveling Salesman problem

what is the shortest path through N cities? A quantum computer differs more from a laptop…

…than a laptop differs from an ABACUS” adapted from Quantum Computer Technologies Science, Dec 2016

Neutral atoms Photonics Neutral atoms, like Photonic qubits ions, store qubits interact via linear within electronic elements states. Interactions through excitation to Rydberg states 1

97%

20 Google, Quantum Diamond Atom Computing PsiQuantum IBM, Rigetti, QCI,.. IonQ, Honeywell Intel, HRL, SQC Microsoft Technologies QuEra ColdQuanta Xanadu

Many qubits, 2D and Linear optical gates, maybe 3D integrated on-chip

Lasers needed, spaghetti No memory, not clear physics, atoms escape how to scale Individual Atoms Atomic (hyperfine) qubit (171Yb+)

= 2 | |1,0 nHF/2p = 12.642 812 118 GHz S1/2 | = |0,0 “idle coherence time = ∞” 171Yb+ Qubit Detection

g/2p = 20 MHz

2 2.1 GHz P1/2

Probability |

369 nm

0 10 20 30 40 50 60 # photons collected in 50 ms

2 | nHF/2p = 12.642 812 118 GHz S1/2 | 171Yb+ Qubit Detection

High-NA collection + SNSPD (J. Kim, Duke) - 6.5% of fluorescence detected - 99.93% qubit detection in 12 ms

g/2p = 20 MHz

2 2.1 GHz P1/2

| Probability

369 nm

0 10 20 30 40 50 60 # photons collected in 50 ms

2 | nHF/2p = 12.642 812 118 GHz S1/2 | 171Yb+ Qubit Manipulation

2 g/2p = 20 MHz P3/2 66 THz

D = 33 THz 2 P1/2

푔1 355 nm (100 MHz, 10psec)

푔2

2 | S1/2

| nHF = 12.642 812 118 GHz

D. Hayes et al., PRL 104, 140501 (2010)

Monroe Group

Photo: Phil Schewe Atomic Physics Lab ENIAC (1946)

МЭСМ (1949)

Colossus (1943)

Nature 583, 10 (2020) Quantum Computer Optical Controller

Full “Quantum Stack” architecture AOM

beam-pointing stabilizer ………………………….. Marko Cetina 32-channel rep rate stabilizer AOM

rf inputs power (200MHz) stabilizer

S. Debnath,... Nature 536, 63 (2016) Laser DOE N. Linke,... PNAS 114, 13 (2017) beam-pointing stabilizer Quantum Computer Optical Controller

Full “Quantum Stack” architecture AOM

beam-pointing stabilizer …………………………..

32-channel rep rate stabilizer AOM

rf inputs power (200MHz) stabilizer

S. Debnath,... Nature 536, 63 (2016) Laser DOE N. Linke,... PNAS 114, 13 (2017) beam-pointing stabilizer Recent Quantum Computer Collaborations

Year Application Reference Collaborator Institute 2013 Frustration and AFM order Science 340, 583 J. Freericks Georgetown 2014 Lieb-Robinson propagation Nature 511, 198 A. Gorshkov NIST 2015 Spin-1 Dynamics Phys. Rev. X 5, 021026 A. Retzker Hebrew University 2016 Manybody Localization Nat. Physics 12, 907 D. Huse, P. Hauke Princeton, Innsbruck 2017 Hidden Shift, Toffoli-3 Gate PNAS 114, 13 M. Roetteler Microsoft, Inc. Grover Nat. Comm. 8, 1918 D. Maslov NSF Toffoli-4 Gate Thesis, Debnath D. Maslov NSF Prethermalization Science Adv. 3, e1700672 Z. Gong, A. Gorshkov NIST Time Crystaline Order Nature 543, 217 N. Yao Berkeley Dynamical Phase Transition Nature 551, 601 A. Gorshkov NIST [[4,2,2]] Error Detection Science Adv. 3, e1701074 K. Brown Duke 2018 Fredkin Gate, Fermi-Hubbard PRA 98, 052334 S. Johri Intel Corp. Bayesian Game QST 3, 045002 N. Solmeyer ARL Qubit Detection ML J. Phys. B 51 174006 M. Hafezi JQI 2019 Full Adder, Parallel CNOTs Nature 567, 61 D. Maslov NSF Generative Modeling ML Science Adv. 5, eaaw9918 A. Perdomo-Ortiz NASA Deuteron VQE Simulation PRA 100, 62319 R. Pooser, O. Shehab ORNL, IonQ Validating stabilizer states Phys. Rev. A 99, 042337 Amir Kalev QuICS UMD Quantum Scrambling Nature 567, 61 B. Yoshida, N. Yao Perimeter, Berkeley Circuit QAOA arXiv:1906.02699 T. Hsieh, S. Johri Perimeter, Intel Corp. Benchmarks and Comparison arXiv: 1905.11349 M. Martonosi Princeton Analog QAOA arXiv:1906.02700 A. Gorshkov, S. Jordan NIST, Microsoft Inc. Quasiparticle Confinement arXiv: 1912.11117 A. Gorshkov NIST Efficient QAOA (Max-Cut, Deuteron) arXiv:1906.00476 Isaac Kim, Omar Shehab Stanford, IonQ Dynamical mean field theory arxiv: 1910.04735 Ross Duncan, Ivan Rungger Cambridge QC, NPL Recent Quantum Computer Collaborations

Year Application Reference Collaborator Institute 2020 Many-body dephasing arXiv: 2001.02477 F. Marquardt MPL Erlangen Quantum walks theory arXiv:2001.11197 B. Radhakrishnan, C. Chandrashekar ARL, Chennai Quantum walks, cellular automaton arXiv:2002.02537 B. Radhakrishnan, C. Chandrashekar ARL, Chennai [[9,1,3]] Bacon/Shor code arXiv:2009.11482 K. Brown Duke NMR Deconvolution in progress E. Demler Harvard Measurement-induced phase xsition in progress M. Gullens, D. Huse, N. Yao NIST, Princeton, Berkeley Classical Verification of QC in progress U. Vazarani, N. Yao, T. Vidick Berkeley, CalTech Cross platform benchmarking in progress Peter Zoller Innsbruck Lattice Gauge Thy in progress Z. Davoudi UMD Ising Scattering in progress Yannick Meurice U. Iowa Circuit-based MBL in progress Sonika Johri Intel Corp. Schwinger model simulation in progress Zohreh Davoudi UMD Envariance measures in progress Wojciech Zurek Los Alamos Para-particle simulationsNorbert Linke in progressMarko Cetina C. M. Alderete,Crystal Blas R.Noel Lara UMD, INAOE Edge-cover problem QAOA in progress B. Sundar, K. Hazzard Innsbruck, Rice Lee-Yang Zeroes (UMD/JQI) in progress(UMD/JQI) Lex Kemper(UMD/JQI) NCSU Triangle game in progressnew faculty @DukeAkimasanewMiyake faculty @Duke UNM Molecular Cluster simulations in progress Nicolas Sawaya Intel Corp. Ring-molecule dynamics Q-Sim in progress Rob Parrish QCWare Chaos-QAOA in progress Gregory Quiroz, O. Shehab APL, IonQ GAN-compression of circuits in progress Xiaodi Wu QuICS UMD QFT- based benchmarking in progress Yannick Meurice U. Iowa Block-diagonalization via Grover in progress Sonika Johri Intel Corp. term-ordered VQE in progress M. Martonosi Princeton Cluster state generation in progress Robert Raussendorf, Vito Scarola UBC, VaTech Block-optimized VQE in progress Peter Zoller Innsbruck A. Gorshkov (JQI/NIST) Exotic Magnetism D. Huse (Princeton) Dynamical Phase Transition with 50+ Qubits S. Johri (Intel)

(1) Prepare spins along 푥 align along 푧 푱 20 (2) Quench spins to 퐻 = ෍ 휎푖 휎푗 + 푩 ෍ 휎푖 |푖 − 푗|훼 푥 푥 푧 푖<푗 푖 order N=53 (3) Measure along 푥 along 푥 18 qubits increase 16 푩/푱

14 avg. largest domain avg. size

12 0 0.5 1.0 1.5 2.0 퐵/퐽 N. Yao (UC Berkeley) Cosmology + Quantum Gravity B. Yoshida (Perimeter) Quantum Scrambling L. Susskind (Stanford)

Scrambling: “complete diffusion” of quantum information, relevant to information evolution in black holes

In 1935, Einstein and Rosen showed that widely- separated black holes can be connected by a tunnel input through space-time, now known as a wormhole qubit |휓ۧ EPR 푈 0ۧ| 0ۧ| EPR Bell Bell Bell † 0ۧ| †EPR 푈 0ۧ| 0ۧ| EPR 휓ۧ| 0ۧ| entanglement Landsman, et al., Nature 567, 61 (2019) output qubit Physicists suspect that the connection in a wormhole Successful teleportation if U scrambles and the connection in quantum entanglement are the same thing, just on a vastly different scale! Quantum Computer Scaling I >100 qubits

Linear shuttling through Shuttling between single zone multiple zones

NIST-Boulder Nature 417, 709 (2002) Univ. Mainz Science Advances 3, e1601540 (2017) Quantum Computer Scaling II >1000 qubits

Plan: Multicore quantum Technology: Integrated photonics and processing switches, SNSPD detector array

QMem QComm

detector optical array switch Making single photons coincidence count rate

beam- splitter 2 photo- photo- 푔 (휏) 138Ba+ detector detector

mJ=+1/2 P1/2 p ~ 4% 649.7nm t (ms) optical D fiber t=10ns 3/2 mJ=+3/2

493.4nm Single 푔 2 (휏0)) S trapped 1/2 138Ba+ atom mJ=+1/2 mJ=-1/2 Higginbottom, et al. (Innsbruck), New J. Phys. 18, 093038 (2016)

ns pulses t (ms) @ 100 kHz C. Crocker, et al., Optics Express 27, 28143 (2019) Making single photons excellent single photon source

beam- splitter p ~ 3% photo- photo- detector detector

t) P. Maunz, et al., Nature (

(2) Physics 3, 538 (2007) g

l=369nm optical fiber -1000 -500 0 500 1000 time delay (ns)

delay (ns)

Single C. Crocker, et al., Optics trapped Express 27, 28143 (2019) 174Yb+ atom 푔 2 (0)

Higginbottom, et al. (Innsbruck), 2ps pulses New J. Phys. 18, 093038 (2016) @ 5.3 MHz 2-photon interference

Tinteg ~ minutes

beam- splitter g(2)(t) p2 ~10-3 photo- photo- detector detector

optical fibers

delay (ns)

Single Single Hong, Ou, Mandel, PRL 59, 2044 (1987) trapped trapped Y.H. Shih & C. O. Alley, PRL 61, 2921 (1988) 174Yb+ atom 1 meter 174Yb+ atom Santori, et al., Nature, 419, 594 (2002) Kaltenbaek, et al, PRL, 96, 240502 (2006) spinless atom Legero, et al., PRL, 93, 070503 (2004). Thompson, et al., Science, 313, 74 (2006). (no qubit) Felinto, et al. Nature Physics, 2, 844 (2006). 2ps pulses Beugnon, et al. Nature, 440, 779 (2006). @ 8.1 MHz P. Maunz, et al., Nature Physics 3, 538 (2007) Photonic Linkage between Atomic Qubits

Hong, Ou, Mandel, PRL 59, 2044 (1987) Heralded coincident events: Y.H. Shih & C. O. Alley, PRL 61, 2921 (1988) Simon & Irvine, PRL 91, 110405 (2003) beam- (H1 & V2) or (V1 & H2) → |↓↑ - |↓↑ L.-M. Duan, et. al., QIC 4, 165 (2004) photo- splitter (H & V ) or (V & H ) → |↓↑ + |↓↑ Y. L. Lim, et al., PRL 95, 030505 (2005) p2 ~10-3 photo- 1 1 2 2 detector 2007: Trapped Ions [Nature 449, 68–71] detector (H1 & H1) or (H2 & H2) → |↓↓ 2013: Trapped Neutrals [PRL 110, 140403] → |↑↑ 2014: NV-diamond [Science 345, 532] (V1 & V1) or (V2 & V2) 2015: Quantum Dots [Nature Phys. 12, 218] 2016: Superconductors [PRX 6, 031036] 1 푅 = 푅푝2 푒푛푡 2 optical fibers Current State-of-art:

푑Ω D. Hucul, et al., Nature 푝 = 휂 푇 = .35 .6 .1 = 2% 퐷 4휋 Phys. 11, 37 (2015) Single Single trapped trapped 푅 = 1 푀퐻푧 C. Balance, et al, Phys. 171Yb+ atom 1 meter 171Yb+ atom Rev. Lett. 124, 110501 −ퟏ 푹풆풏풕 ≈ ퟏퟖퟎ 풔풆풄

2ps pulses Soon: ~ퟏퟎퟒ 풔풆풄−ퟏ …slow, but we have time @ 8.1 MHz Vision I: Modular Scaling with Photonic Interconnects

0.001 Hz before ~200 Hz now ~10 kHz soon?

Duan and Monroe, Rev. Mod. Phys. 82, 1209 (2010) Li and Benjamin, New J. Phys. 14, 093008 (2012) Monroe, et al., Phys. Rev. A 89, 022317 (2014) Ion Trap QC Path to Scale 2018 2016 Bench Lab scale scale 2020 2m

10m 2025 2021 0.5m Chip 2023 0.1m scale Rackmount 0.01m scale IonQ was founded in 2015 by Chris Monroe and Jungsang Kim, headquartered in College Park, MD

IonQ is a leader in quantum computing, with technology based on individual atomic qubits, having high quality and reconfigurable quantum operations. We have a clear scaling roadmap to tackle problems that are impossible with classical computers.

We have built several generations of full-stack quantum computer systems, with cloud access via commercial servers. www.ionq.com Venture Investors College Park, MD ($84M raised)

70 employees New Enterprise Google Associates Ventures Quantum computer www.ionq.com IonQ Systems on the cloud autoloading register

N=24 qubits preprogrammed

Quantum Computing zone

Loading zone Lower Errors through Encoding

⟹ 훼|0ۧ + 훽|1ۧ

error prob. 푝

error prob. 푝 (per qubit) 01011ۧ| + 10110ۧ| + 01101ۧ| + 11111ۧ| 10100ۧ| + 01001ۧ| + 10010ۧ| + 00000ۧ| 00111ۧ| − 11001ۧ| − 00100ۧ| − 10101ۧ|+ 11000ۧ| − 00110ۧ| − 11011ۧ| − 01010ۧ|+ 훼 −|11101ۧ − |00011ۧ − |11110ۧ − |01111ۧ + 훽 −|00010ۧ − |11100ۧ − |00001ۧ − |10000ۧ 11010ۧ| + 10111ۧ| − 10011ۧ| − 01110ۧ|− 00101ۧ| + 10111ۧ| − 01100ۧ| − 10001ۧ|−

C. Shannon (classical) 2 P. Shor 푝 ⟹ 퐶푝 Quantum Error Correction R. Calderbank A. Steane University Industry ? ✓No problem with quantum physics  Not so familiar with quantum physics ✓Take research “where it goes”  May not build things for science  Don’t “build” things here National ✓ Engineering, manufacturing, reliability Laboratory

✓ No problem with quantum physics ✓ Research for science and applications ✓Engineering, manufacturing, reliability  Little history in the field (for now) U.S. National Quantum Initiative Act (2018) The NPI Team behind the NQI

H.R. 6227

Ed White NPI

Laura Kolton OSA David Lang Mike Raymer OSA (now at Indiana U) U Oregon

Jennifer O’Bryan SPIE Ken Robert Marko Brown Calderbank Cetina A Quantum Computer User Facility that will • Build quantum computers from the highest performance components Jungsang Chris Crystal Kim Monroe Noel • Use quantum computers for science • Co-design next generation quantum • Physics • Mathematics computers based on scientific use cases • Electrical & • Computer Computer Science • Translate quantum technology to national Engineering and commercial societal needs • Chemistry