Nicolás Pulido Christian Ospelkaus Physikalisch-Technische Bundesanstalt, Braunschweig Institut für Quantenoptik, Leibniz Universität Hannover Towards a Small - Scale Trapped - Ion Quantum Processor Based on Near - Field Microwave Quantum Logic Gates
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Nicolás Pulido
Christian OspelkausPhysikalisch-Technische Bundesanstalt, Braunschweig
Institut für Quantenoptik, Leibniz Universität Hannover
Towards a Small-Scale
Trapped-Ion Quantum
Processor Based on
Near-Field Microwave
Quantum Logic Gates
INTRODUCTION
2
Qubits
Classical unit of information
Quantum degree of freedom
Superposition principle
“0”+
- “1”
Logic gates
Reversible operations
Uȁ ↑, 0
ȁ ↓, 1
1
2ȁ ↑ + ȁ ↓
3
748 957 416 402 469 183 253 951 … …
x 593 165 415 037 541 213 576 874 … …
… … … … …=
890 589 346 128 763 258 109 854 … …
… x … x … x …=
Basis for public key cryptography
(RSA)…Basis for secure websites,
digital signatures,
encrypted email,…
Mare Nostrum, Barcelona
Quantum computers and cryptography
4
Quantum computers and cryptography
890 589 346 128 763 258 109 854 … …
… x … x … x …=
(well, it can be done in polynomial time…)
Peter Shor
𝒰⨂⨂⋯
5
Quantum simulation
n=128 spins: 2n ≈ 3.4∙1038 entries
2n+5 ≈ 1040 Bits (32 bits per complex number)
22n+10 Bits ≈ 1080 Bits
Feynman, 1982:
Quantum computers
(and simulators)
can do much better!
State vector for n spins
Compute evolution (matrix)
Number of protons in the universe: ≈ 1080Crab nebula
The challenge
6
State detection
2,2
1,1
1,1
1,2 0,2
1,2 2,2
0,1
Be9
2/1S
2/3P
Notation: FmF,
3,3
313 nm
0
1
a qubit!
7
Raman
laser beams
State initialization via optical pumping
Preparation of arbitrary one-ion states via Raman laser beams
“Single qubit gate”
State manipulation
GHz101
Raman process
e
313 n
m
GHz80
8
Coupling to the motion
+n=0
n=1
n=2
n=3
Motional
Degree of Freedom
Internal
Degree of Freedom
Sideband transitions Basis for:
Ground state cooling
Fock, “cat” and coherent
states of motion
Quantum logic
Aluminum ion clock
n=0
“red” sideband
“blue” sideband
carrier
n=1n=2n=3
n=0n=1n=2n=3
Diedrich et al., PRL 62, 403 (1989)
9
Raman
laser beams + +
Normal modes
Description of normal modes as harmonic oscillators
Sideband transitions for normal modes
10
Entangling quantum logic gates
ninn 2
1Entangled state!
Mølmer and Sørensen, PRL 82, 1835 (1999)
Solano et al., PRA 59, 2539 (1999)
Sackett et al., Nature 404, 256 (2000)
Raman
laser beams
n
n
1 n 1 n
n n
1 n 1 n
1 n
1 n
1 n
1 n
11
A scalable, solid-state based platform for ion qubits
D. Wineland et al., J. Res. NIST 103 (1998)
D. Kielpinski et al., Nature 417 (2002)
++++
++ ++++
Two-qubit gate
processing
storage
processing
detection
laser
read-outread-out
Single-qubit gate
DCRF
12
A SCALABLE PLATFORM FOR
TRAPPING AND MANIPULATION
13
Surface-electrode ion traps for scalability
DC electrodes
RF electrodes
Field lines:
Chiaverini et al., Quant. Inf. Comp. 5, 419 (2005)
Seidelin et al., Phys. Rev. Lett. 96, 253003 (2006)
14
Trap fabrication
PTB cleanroom center,
thanks to divisions 2 &4!
A. Bautista-Salvador et al., NJP 21, 043011 (2019); patent DE 2018 10 111 220
15
Growing of thick metal films
A. Bautista-Salvador et al., NJP 21, 043011 (2019); patent DE 2018 10 111 220
16
Multi-Layer Ion Trap
17A. Bautista-Salvador et al., NJP 21, 043011 (2019); patent DE 10 2018 111 220
17
Choice of metals for electrodes
Hide dielectrics as much as possible
Choice of substrate materials
Scalable multilayer method
Fabrication requirements
+
-
RF loss
Heatconductivity
4K vs. 300KMachineability
Silicon, Aluminum
Nitride, Quartz,
Sapphire, …
18
Layer thickness & supported current
( → also: „atom chips“)
Integration (electronics, optics)
Turnaround, yield
People
Fabrication requirements
Jonathan
Morgner
Amado
Bautista-
Salvador
Martina
Wahn-
schaffe
MAIUS-B launch,
Esrange
> 80%
1 day (SL)
4 weeks (ML)
A. Bautista-Salvador et al., NJP 21, 043011 (2019); patent DE 10 2018 111 220
19
Yes! I am an inventor!
20
Vision: trap foundry service!
Are you interested in a surfacetrap? Let us know! We canpossibly make it for you…
NEAR-FIELD MICROWAVE
QUANTUM GATES
21
Ion-trap multi-qubit quantum logic
Internal states
as qubits
Motion as a
quantum buse
Raman process
+ +
(Two-level atom) (Harmonic oscillator)
Sideband
transitions
n=0n=1n=2n=3
n=0n=1n=2n=3
Entangling gates,
clocks, …
Raman lasers?
Why not usemicrowaves?≈ GHz
200−800nm
22
MAGIC
Mintert and Wunderlich, PRL 87, 257904 (2001)
23
Near-field idea
Free-space laser field
Basic near-field idea
Ideal near-field
geometry
𝐸
𝐸
𝐼𝑀𝑊
𝐼𝑀𝑊𝐼𝑀𝑊
200 − 800 nm
𝑥0 = ℏ/(2𝑚𝜔trap) ≈ 10 nm
𝑥0
𝐵𝐵 − ∆𝐵
Ospelkaus et al., PRL 101, 090502 (2008)
See also: Mintert and Wunderlich, PRL 87, 257904 (2001)