To further corroborate this successful entanglement creation, we transferred only one photon to l = T300 and measured the other photon
in the polarization bases. The measured witness
value was 1.628 T 0.004. Therefore, our results
demonstrate that single photons can carry 300ħ
of OAM (where ħ is Planck’s constant divided
by 2p) and that entanglement between two photons differing by 600 in quantum number can
be achieved. Even in classical optics, the highest
value of OAM that had been created with an
SLM was l = 200 (30).
Apart from the fundamental interest of entangling high quantum numbers, we also demonstrate the use of high-OAM entanglement for
remote sensing. For this we use the same method as before for creating high-OAM entangled
states (folded interferometric scheme including
SLM) and analyzing them (slit wheel method).
When we transfer one photon to high OAM values and keep the other in its polarization state,
the pair can be used to remotely measure an angular rotation with a precision that is increased
by a factor l relative to the situation when only
polarization-entangled photon pairs are used
(Fig. 4) (22). This can lead to notable improvements for applications in the field of remote
sensing, especially where low light intensities are
required, such as in biological imaging experiments with light-sensitive material. An analogous
improvement can be achieved classically if diagonally or circularly polarized light enters our transfer setup. However, the important difference is that
entanglement enables the measurements to be
done remotely, with the photons being spatially
separated or even in unknown locations at some
Our approach could be generalized to higher-dimensional entanglement for spatial modes—
for example, by starting with higher-dimensional
(hybrid) entanglement and a more complex interferometric scheme. Such a development would
have potential benefits in applications such as
quantum cryptography, quantum computation,
and quantum metrology.
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Acknowledgments: Supported by the European Research
Council (advanced grant QIT4QAD, 227844) and the Austrian
Science Fund (FWF) within the Special Research Programs
(SFB) F40 (Foundations and Applications of Quantum Science;
FoQuS) and W1210-2 (Vienna Doctoral Program on Complex
Quantum Systems; CoQuS). R.F. participated in the design
and building of the experimental apparatus, collected and
analyzed the data, and wrote the manuscript. R.L., C.S., and
S.R. participated in the design and building of the experiment
and assisted on the experimental side. W.N.P., S.R., and
M.K. assisted on the theoretical side. A.Z. initiated the work
and supervised the experiment. All authors contributed to
conceiving the experiment, discussing the results, and
contributing to the final text of the manuscript.
Materials and Methods
9 July 2012; accepted 20 September 2012
Efficient Hybrid Solar Cells
Organometal Halide Perovskites
Michael M. Lee,1 Joël Teuscher,1 Tsutomu Miyasaka,2 Takurou N. Murakami,2,3 Henry J. Snaith1*
The energy costs associated with separating tightly bound excitons (photoinduced electron-hole
pairs) and extracting free charges from highly disordered low-mobility networks represent
fundamental losses for many low-cost photovoltaic technologies. We report a low-cost,
solution-processable solar cell, based on a highly crystalline perovskite absorber with intense
visible to near-infrared absorptivity, that has a power conversion efficiency of 10.9% in a
single-junction device under simulated full sunlight. This “meso-superstructured solar cell”
exhibits exceptionally few fundamental energy losses; it can generate open-circuit photovoltages
of more than 1.1 volts, despite the relatively narrow absorber band gap of 1.55 electron volts.
The functionality arises from the use of mesoporous alumina as an inert scaffold that structures
the absorber and forces electrons to reside in and be transported through the perovskite.
generated by the solar cell under simulated air
mass (AM) 1.5 solar illumination of 100 m W cm−2
(9). For instance, gallium arsenide (GaAs) solar
cells exhibit Voc of 1.11 V and an optical band
gap of 1.4 eV, giving a difference of ~0.29 eV
(2). For dye-sensitized and organic solar cells,
this difference is usually on the order of 0.7 to
0.8 eV (2, 9). For organic solar cells, such losses
are predominantly caused by their low dielectric
constants. Tightly bound excitons form, which
require a heterojunction with an electron accep-
tor with a large energy offset to enable ion-
ization and charge separation (10, 11). Likewise,
dye-sensitized solar cells (DSSCs) have losses,
both from electron transfer from the dye (or ab-
sorber) into the TiO2, which requires a certain
“driving force,” and from dye regeneration from
An efficient solar cell must absorb over a broad spectral range, from visible to near- infrared (near-IR) wavelengths (350 to
~950 nm), and convert the incident light effec-
tively into charges. The charges must be collected
at a high voltage with suitable current in order to
do useful work (1–8). A simple measure of solar
cell effectiveness at generating voltage is the dif-
ference in energy between the optical band gap
of the absorber and the open-circuit voltage (Voc)
1Clarendon Laboratory, Department of Physics, University of
Oxford, Oxford OX1 3PU, UK. 2Graduate School of Engineering, Toin University of Yokohama, 1614 Kurogane, Aoba,
Yokohama 225-8503, Japan. 3Research Center for Photovoltaic
Technologies, National Institute of Advanced Industrial Science and Technology, Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki
*To whom correspondence should be addressed. E-mail: