Chin. Phys. B Vol. 24, No. 4 (2015) 043701
Efficient loading of a single neutral atom into
an optical microscopic tweezer
∗
He Jun(何 军)
†
, Liu Bei(刘 贝), Diao Wen-Ting(刁文婷),
Wang Jie-Ying(王杰英), Jin Gang(靳 刚), and Wang Jun-Min(王军民)
‡
State Key Laboratory of Quantum Optics and Quantum Optics Devices and Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China
(Received 12 August 2014; revised manuscript received 9 October 2014; published online 10 February 2015)
A single atom in a magneto–optical trap (MOT) with trap size (hundreds of micrometers) can be transferred into an
optical microscopic tweezer with a probability of ∼100%. The ability to transfer a single atom into two traps back and
forth allows us to study the loading process. The loading probability is found to be insensitive to the geometric overlap of
the MOT and the tweezer. It is therefore possible to perform simultaneously loading of a single atom into all sites of the
tweezer array for many qubits. In particular, we present a simulation of the one-dimensional and two-dimensional arrays
of an optical microscopic tweezer. We find the same qualitative behavior for all of the trap parameters.
Keywords: single atom, magneto–optical trap, optical tweezer, loading process
PACS: 37.10.De, 37.10.Jk, 25.20.Dc DOI: 10.1088/1674-1056/24/4/043701
1. Introduction
Quantum computer and quantum information storage
are built up from multiple microscopic physical systems.
The most advanced experimental demonstrations at this
time include trapped ions,
[1]
nuclear magnetic resonan-
ce,
[2,3]
superconductors,
[4,5]
and quantum dots in semicon-
ductors.
[6–8]
With some of them, significant achievements in
quantum computing have already been accomplished. Neutral
atoms represent another promising approach,
[9]
which shares
many features in common with trapped ion systems, includ-
ing long-lived encoding of quantum information in atomic
hyperfine states, week-decoupled with the environment. Us-
ing laser cooling techniques, countable numbers of neutral
atoms can be trapped in an optical microscopic tweezer (far-
off-resonance optical dipole trap), which can realize the full
control of internal and external degrees of freedom.
[10,11]
A
single atom trapped in microscopic tweezer can serve as a
qubit.
[12–14]
Using two-dimensional arrays of refractive or
diffractive micro-lenses, arrays of tweezers can be achieved,
thus two-dimensional register of an atomic qubit can be ob-
tained by loading a single neutral atom into these individu-
ally traps.
[15–17]
Moreover, the neutral atoms of two qubits are
excited to highly excited Rydberg states that can be used to
implement the quantum controlled-CNOT gate or create the
entanglement.
[18,19]
Arrays of individual neutral atoms in traps
with strong interaction are promising candidates for quantum
computing experiments and quantum information processing.
A set of criteria for implementing a quantum computing
device require many qubits to be initialized at the same time,
which depends on preparation of many microscopic tweezers
for single atom occupancy. Several approaches have demon-
strated the ability to load a single atom into a single tweezer.
However, when many microscopic tweezers immerse in a large
size magneto–optical trap (MOT), due to the extremely small
trapping volume of tweezer compared with the MOT size,
loading the preset number of atoms from the MOT into the
multiple and individual site demanded is difficult. Although
some experimental results have been demonstrated, the load-
ing process has not been experimentally studied in detail. In
this work we study the dynamics of loading a single atom
trapped in a large size MOT into a microscopic tweezer. To
study the loading process, we load only one atom trapped in
the MOT into a microscopic tweezer and monitor the dynam-
ics. Moreover, we report the direct observation of dependence
of loading probability on the geometric overlap between the
MOT and tweezer centers.
2. Experimental setup
A schematic diagram of the experimental setup is shown
in Fig. 1(a). We control the background cesium atom num-
ber in the working area by light-induced atom desorption. In
our MOT system cooling/trapping laser beams and repump-
ing laser beams are provided by two homemade 852-nm grat-
ing external-cavity diode lasers in the Littrow configuration.
The two pairs of beams in horizontal plane intersect with
the glass cell at an angle of 60
◦
. The cooling laser of the
(6S
1/2
F
g
= 4)–(6P
3/2
F
e
= 5) transition is stabilized using the
modulation-free polarization spectroscopic locking scheme.
∗
Project supported by the National Major Scientific Research Program of China (Grant No. 2012CB921601) and the National Natural Science Foundation of
China (Grant Nos. 61205215, 11274213, and 61475091).
†
Corresponding author. E-mail: hejun@sxu.edu.cn
‡
Corresponding author. E-mail: wwjjmm@sxu.edu.cn
© 2015 Chinese Physical Society and IOP Publishing Ltd http://iopscience.iop.org/cpb http://cpb.iphy.ac.cn
043701-1