ICAP2012@France Poster Presentation Mo-105

1. One-way quantum computation with ultra-narrow optical transition of 171
Yb atoms (Mo-105)
Akimasa Nakamoto1,*, Martin Miranda1, Yuki Okuyama1, Atsushi Noguchi1,†, Masahito Ueda2, and Mikio Kozuma1
1. Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo, Japan
2. University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
*nakamoto.a.aa@m.titech.ac.jp, †Present Affiliation: Osaka University
1. Our plan 2. Review:
Conventional technique for making a cluster state for electron spins
We are planning to implement a quantum computer with 171Yb atoms which have nuclear spin of A cluster state has been successfully created for Rubidium atoms through controlled collisions
1/2 in the ground state. Magnetic moment of the nuclear spin is 2000 times smaller than that of which was implemented by using electronic spin dependent optical potential[2].
the electronic spin. This fact leads to a merit of long coherence time, but also makes it diffcult to
realize two qubits gate operation using dipole-dipole interaction.
e-

e-
171
Yb
Our strategy: Cluster computation

Why: Only one time qubits interaction is required. [Xe]4f 6s 14 2
To implement a one-way quantum computation

Operation 1.
Produce highly entangled multi-particle states (Cluster states)
 Fine   Detuning   Hyperfine  
 C
 2 
 3 
 0 1 z  1 1 0 2  z  1 2  0   n 1
 z  1 n 1  0 n  1 n 
n 
Hyperfine 2
P3/2
Operation 2. Fine 500 MHz
300 GHz  Detuning   Hyperfine
Apply unitary transformation and observe each qubit in sequence. 2
P1/2
800 MHz
Hyperfine   
dependency is lost
[1]Raussendorf, R. & Briegel, H. J. A one-way quantum computer. Phys. Rev. Lett. 86, 5188-5191 (2001). J I
1 3
 
S1/2
2
2 2 1 1
J I mj   mj  

1 3

2 2
How to realize qubits interaction?
2 2
[2] Olf Mandel, Markus Greiner, Artur Widera, Tim Rom, Theodor W. Haensch & Immanuel Bloch, Controlled collisions for multi-particle
entanglement of optically trapped atoms, Nature 425, 937-940 (2003)
3. How to make nuclear spin dependent potential? 4. How to realize qubits interaction?
Comparison of two approaches to make an optical lattice (Potential depth 10μK, Life time 1 sec). μm=2.7μB
In the nuclear spin dependent potential,
Hyperfine 3 1 1 3 3 3
mF '   mF '  
Γ/ 2π = 29 MHz 350 MHz mF '   mF '   mF '   mF '   superposition between S0 and a small
1
P1
1 F’ = 1/2
3
P2 2 2 2 2
F’ = 3/2 3
P2(F’ = 3/2)
2 2
399 nm
F’ = 3/2 507 nm amount of P2 is generated.
3
Detuning Hyperfine
-75 THz
443 nm
F’ = 5/2
0  mF 1/ 2  1 / 2   mF '3 / 2  3 / 2  
Power 1W Power 400mW 1  mF 1/ 2  1 / 2   mF '3 / 2  3 / 2 S0(F = 1/2)
1
Waist 60μm Waist 30μm 1 1
mF   mF  
2 2
 
 
S0
1
mF  
1
2
mF  
1
2
S0
1
1 1
mF   mF  
Hyperfine dependency is lost 2 2
r
P1
1  Hyperfine   Detuning   1 0 To achieve a π phase shift:
399 nm
6.6 GHz -1 MHz 25 mHz 0  m 4
2 r = 30 nm,
443 nm
Enegy Shift ~  
4 r 3 Power = 400 mW, Waist = 30μm,
Ultra-narrow optical transition is very useful Detuning = 2π × 1 MHz,
for preparing a nuclear spin dependent Potential = 4 μK (17Er),
potential! ρee = |ε|2 = 0.07,
S0
1
Interaction Time = 5 ms.
J=0
5. Coherence time vs interaction time 6. Single site access
When we create a cluster state, mixing between the 1S0 and 3P2 states is required. However, By focusing a far detuned laser light into a specific site, a light shift can be
such a mixing leads to decoherence of the qubit, since the 3P2 state has a large magnetic induced. The pumping light, with its wavelength of 507nm, excites the single
moment. By changing the detuning of the lattice beam by factor of ∼ 8 MHz, we can atom in that specific site to the 3P2 metastable state in a spin dependent manner.
switch off such mixing, while Using the cyclic transition
(sec)
maintaining the lattice potential, Cluster interaction time between 3P2 and 3D3 states
10 D3
3
5 MHz
since the potential is induced by S0 1
(494nm), we can collect
1 494 nm
to P1 transition.
1
fluorescence from the atom and
Decoherence time
0.1 perform the projective P2
3 25 mHz
P1
1 0.01 measurement.
28 MHz
0.001 x
(MHz)
2 4 6 8 10
0
5 MHz
399 nm D3
3
-2 Potential due to 1S0 -> 3P2
3
494 nm
P2 25 mHz
-4
-6
Related presentation
3
P1 181 kHz -8 Tu-107 “Resolution assessment of a fluorescence microscope for observing
507 nm -10 single ytterbium atoms trapped in two-dimensional optical lattice”
556 nm
3
P0
-12
578 nm
-14 Potential due to 1S0 -> 1P1 Th-105 “All optical formation of Ytterbium two-dimensional
1
S0
(μK) quasi-condenstate near surface of solid immersion lens”
Interaction ON Interaction OFF