2. University of Oxford, U.K.*
Q.Tech.Roadmap: Quantum Computing
David Lucas
Ion Trap QC group
University of Oxford, U.K.*
(on behalf of Daniel Esteve, CEA-Saclay and QUTE working group)
info taken from QT Roadmap sections 1.1 and 2.1
EU list of QT research groups has ~440 entries, many interested in QC

3. University of Oxford, U.K.*
Q.Tech.Roadmap: Quantum Computing
David Lucas
Ion Trap QC group
University of Oxford, U.K.*
(on behalf of Daniel Esteve, CEA-Saclay and QUTE working group)
info taken from QT Roadmap sections 1.1 and 2.1
EU list of QT research groups has ~440 entries, many interested in QC
* full member of the E.U. until at least March 2019 !

4. Kaiser Wilhelm Memorial Church, Berlin

5. QC intro + motivation Quantum Computing in an nut U
quantum register : set of quantum bits
quantum bit : two basis states
any arbitrary superposition is a possible state
a N qubit register has 2N basis states:
any arbitrary superposition of basis states can exist
The register of a quantum processor evolves by applying quantum gates to qubits
QM being linear
the evolution can be
massively parallel U
I X > + I X > + I X> + ...
U I X > + U I X > + U I X> + ...
But readout only
delivers a N bit answer
The art of QC:
I SOL >
I X >
measurement
Factorization algorithm (1994)
Integer N
Runtime
best known classical
Shor
Peter Shor
How many qubits for overcoming
a classical computer ?
The most advanced classical computers & codes
can simulate approx. 45 interacting qubits
a QC with ideal qubits could
out-perform classical computers
(for some tasks)
A QC is « the most powerful computer allowed by the laws of physics » (as far as we know!).
But it is *very* difficult technology, and the Universal QC is still a long-term (>10 yrs) objective.

6. The error correction mountain
log10(no.operations)
log10(scale-up)
log10(gate error)
Overhead and noise threshold of fault-tolerant quantum error correction,
A.M.Steane, PRA 2003

7. Example QC hardware platforms
superconducting circuits
trapped atomic ions
electronic semiconductor qubits
linear optics
impurity spins in solids (e.g. NV centres)
blue: usually cryogenic
red: usually room temp.

8. Some examples of state-of-the-art
log10 (no.operations)
log10 (no.qubits)
log10 (error)
superconducting circuits (cryo.)
semiconductor qubits (cryo.)
trapped ions (room temp.)

9. Some examples of state-of-the-art
log10 (no.operations)
log10 (no.qubits)
log10 (error)
1-qubit gate
memory
initialisation, readout
1-qubit gate
superconducting circuits (cryo.)
semiconductor qubits (cryo.)
trapped ions (room temp.)
initialisation
1-qubit gate

10. Some examples of state-of-the-art
log10 (no.operations)
log10 (no.qubits)
log10 (error)
1-qubit gate
memory
initialisation, readout
1-qubit gate
2-qubit gate
2-qubit gate (in 5-qubit device)
5 qubits, arb. control
20 qubits, limited control
superconducting circuits (cryo.)
semiconductor qubits (cryo.)
trapped ions (room temp.)
initialisation
1-qubit gate

11. Partial history of classical computing
1860s designs for a mechanical computer (Babbage & Lovelace)
1930s functioning mechanical computers (Zuse)
1940s electronic valve-based computers (Turing & Flowers)
1947 invention of transistor (Bardeen, Brattain & Shockley)
1959 development of first integrated circuits (Kilby)
1971 integrated circuit CPU (Intel 4004)
feature size (nm)
no. of transistors per chip
year
fs = feature size, Nt = no. transistors per chip for DRAMs
From “Evolutionary Model of Moore’s Law”, Joachim Kaldasch, EBC Hochschule Berlin, ISRN Economics, , (2014).

12. Partial history of 2-qubit gates
superconducting qubits
ions: laser gates
Turchette et al.
Sackett et al.
Rowe et al.
Leibfried et al.
Benhelm et al.
*Ballance et al.
*Gaebler et al.
*Steffen et al.
*DiCarlo et al.
*Chow et al.
*Barends et al.
* exclude SPAM errors

13. Partial history of 2-qubit gates
ions: far-field m.w.
superconducting qubits
ions: near-field microwave
ions: laser gates
Near-field microwave: 100x progress is one step! (Roughly 10x from “engineering”, 10x from “physics”).
Turchette et al.
Sackett et al.
Rowe et al.
Leibfried et al.
Benhelm et al.
*Ballance et al.
*Gaebler et al.
*Steffen et al.
*DiCarlo et al.
*Chow et al.
*Barends et al.
Ospelkaus et al. *Harty et al.
*Khromova et al.
*Weidt et al.
* exclude SPAM errors

14. Partial history of 2-qubit gates
ions: far-field m.w.
superconducting qubits
ions: near-field microwave
ions: laser gates
Near-field microwave: 100x progress is one step! (Roughly 10x from “engineering”, 10x from “physics”).
Turchette et al.
Sackett et al.
Rowe et al.
Leibfried et al.
Benhelm et al.
*Ballance et al.
*Gaebler et al.
*Steffen et al.
*DiCarlo et al.
*Chow et al.
*Barends et al.
Ospelkaus et al. *Harty et al.
*Khromova et al.
*Weidt et al.
* exclude SPAM errors

15. Quantum networking

17. “Climbing Mount Impossible”
log10(no.operations)
log10(scale-up)
log10(gate error)
You are here
Overhead and noise threshold of fault-tolerant quantum error correction,
A.M.Steane, PRA 2003

18. NQIT: Networked Quantum Information Technology
Network of 20 ion traps each with 20 qubits “The Q20:20 Engine”

20. Sr/Ca Next steps: mixed-species Ca43/Sr88 Ca/Sr wobble gate
laser diagnostics
controllers & lock electronics
diode lasers (422,1033, 1092nm)
switching AOMs
Rack-mount Sr+ laser system
Sr-88 / Ca-40
Ca/Sr gate error
scattering error
heating rate error
total error
wobble gate
P=50mW per beam, w=27um
out-of-phase mode 3.07MHz
heating rate 50/sec (estimate)
For t_g<200us, Raman beam power constant (5mW per beam, w_0=27um) and Raman detuning varied.
For t_g>200us, Raman detuning constant and power varied (as scattering error is negligible in this regime).
Photon scattering error limit (from scattering to D states) is 0.5e-4 (CJB thesis).

22. title