TY  - JOUR
A1  - Jechow, Andreas
A1  - Norton, B. G.
A1  - Händel, S.
A1  - Blums, V.
A1  - Streed, E. W.
A1  - Kielpinski, D.
T1  - Controllable optical phase shift over one radian from a single isolated atom
JF  - Physical review letters
N2  - Fundamental optics such as lenses and prisms work by applying phase shifts of several radians to incoming light, and rapid control of such phase shifts is crucial to telecommunications. However, large, controllable optical phase shifts have remained elusive for isolated quantum systems. We have used a single trapped atomic ion to induce and measure a large optical phase shift of 1.3 +/- 0.1 radians in light scattered by the atom. Spatial interferometry between the scattered light and unscattered illumination light enables us to isolate the phase shift in the scattered component. The phase shift achieves the maximum value allowed by atomic theory over the accessible range of laser frequencies, pointing out new opportunities in microscopy and nanophotonics. Single-atom phase shifts of this magnitude open up new quantum information protocols, in particular long-range quantum phase-shift-keying cryptography. DOI: 10.1103/PhysRevLett.110.113605
Y1  - 2013
U6  - https://doi.org/10.1103/PhysRevLett.110.113605
SN  - 0031-9007
VL  - 110
IS  - 11
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Jechow, Andreas
A1  - Seefeldt, Michael
A1  - Kurzke, Henning
A1  - Heuer, Axel
A1  - Menzel, Ralf
T1  - Enhanced two-photon excited fluorescence from imaging agents using true thermal light
JF  - Nature photonics
N2  - Two-photon excited fluorescence (TPEF) is a standard technique in modern microscopy(1), but is still affected by photodamage to the probe. It has been proposed that TPEF can be enhanced using entangled photons(2,3), but this has proven challenging. Recently, it was shown that some features of entangled photons can be mimicked with thermal light, which finds application in ghost imaging(4), subwavelength lithography(5) and metrology(6). Here, we use true thermal light from a superluminescent diode to demonstrate TPEF that is enhanced compared to coherent light, using two common fluorophores and luminescent quantum dots, which suit applications in imaging and microscopy. We find that the TPEF rate is directly proportional to the measured(7) degree of second-order coherence, as predicted by theory. Our results show that photon bunching in thermal light can be exploited in two-photon microscopy, with the photon statistic providing a new degree of freedom.
Y1  - 2013
U6  - https://doi.org/10.1038/NPHOTON.2013.271
SN  - 1749-4885
SN  - 1749-4893
VL  - 7
IS  - 12
SP  - 973
EP  - 976
PB  - Nature Publ. Group
CY  - London
ER  -