| 1. |
- Amari, Atia, et al.
(författare)
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Towards an efficient atomic frequency comb quantum memory
- 2010
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 130:9, s. 1579-1585
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Konferensbidrag (refereegranskat)abstract
- We present an efficient photon-echo experiment based on atomic frequency combs [Phys. Rev. A 79 (2009) 052329]. Echoes containing an energy of up to 35% of that of the input pulse are observed in a Pr3+ -doped Y2SiO5 crystal. This material allows for the precise spectral holeburning needed to make a sharp and highly absorbing comb structure. We compare our results with a simple theoretical model with satisfactory agreement. Our results show that atomic frequency combs has the potential for high-efficiency storage of single photons as required in future long-distance communication based on quantum repeaters. (c) 2010 Elsevier B.V. All rights reserved.
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| 2. |
- Lovric, Marko, et al.
(författare)
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Hyperfine characterization and spin coherence lifetime extension in Pr3+:La-2(WO4)(3)
- 2011
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 84:10
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Tidskriftsartikel (refereegranskat)abstract
- Rare-earth ions in dielectric crystals are interesting candidates for storing quantum states of photons. A limiting factor on the optical density and thus the conversion efficiency is the distortion introduced in the crystal by doping elements of one type into a crystal matrix of another type. Here we investigate the system Pr3+:La-2(WO4)(3), where the similarity of the ionic radii of Pr and La minimizes distortions due to doping. We characterize the praseodymium hyperfine interaction of the ground-state (H-3(4)) and one excited state (D-1(2)) and determine the spin Hamiltonian parameters by numerical analysis of Raman-heterodyne spectra, which were collected for a range of static external magnetic-field strengths and orientations. On the basis of a crystal-field analysis, we discuss the physical origin of the experimentally determined quadrupole and Zeeman tensor characteristics. We show the potential for quantum memory applications by measuring the spin coherence lifetime in a magnetic field that is chosen such that additional magnetic fields do not shift the transition frequency in first order. Experimental results demonstrate a spin coherence lifetime of 158 ms - almost 3 orders of magnitude longer than in zero field.
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| 3. |
- Sabooni, Mahmood, et al.
(författare)
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Cavity-enhanced storage-preparing for high-efficiency quantum memories
- 2013
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Cavity-assisted quantum memory storage has been proposed for creating efficient (close to unity) quantum memories using weakly absorbing materials. Using this approach, we experimentally demonstrate a significant (similar to 20-fold) enhancement in quantum memory efficiency compared to the no cavity case. A strong dispersion originating from absorption engineering inside the cavity was observed, which directly affects the cavity line width. A more than three orders of magnitude reduction of cavity mode spacing and cavity line width from GHz to MHz was observed. We are not aware of any previous observation of several orders of magnitude cavity mode spacing and cavity line width reduction due to slow light effects.
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| 4. |
- Sabooni, Mahmood
(författare)
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Efficient Quantum Memories Based on Spectral Engineering of Rare-Earth-Ion-Doped Solids
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main aim of the present thesis is to demonstrate the efficient quantum memories for light employing coherent processes in rare-earth-ion-doped crystals. Rare-earth (RE) ions between lanthanum, with atomic number 57, and lutetium, with atomic number 71, have a partly filled 4f shell, which is spatially inside the full shells 5s, 5p, and 6s. Therefore, 4f-4f transitions are shielded from environmental noise. Less noise means longer lifetime and coherence times and, when the crystals are cooled down to about 4 K, these can be about 8 orders of magnitude longer than what is typical for electronic transitions in solids. In quantum information processing, we are looking for physical systems which are isolated from the environment and consequently have good coherence properties. The long coherence time of both optical and spin transitions, is the main attraction of rare-earth ions for quantum information processing. In the present thesis, we map a quantum state of light employing a 4f-4f transition of praseodymium doped in yttrium silicate. We mainly employed the ensemble approach and the atomic frequency comb (AFC) protocol for quantum memory demonstrations. Among several parameters that define quantum memory performance, we mostly focused on quantum memory efficiency. The overall memory efficiency is simply defined as the energy of the pulse recalled from the memory divided by the energy of the pulse sent in for storage in the memory. To maximize quantum memory efficiency, most protocols require high optical depth. This is a limitation for materials with rather good coherence properties but low optical depth. In the research described in the present thesis, we combined the use of a low finesse cavity and the ensemble approach and designed an impedance-match cavity to obtain the advantages of both approaches and thereby to implement an efficient quantum interface in a weakly absorbing solid-state medium. Based on the cavity configuration, we obtained 56% storage and retrieval efficiency, which is the highest storage and retrieval efficiency based on the AFC protocol reported in the research so far. In the present thesis, we demonstrated a narrow-band (about 2 MHz) spectral filter with a >30 dB intensity absorption/transmission ratio, which is based on the large (6 orders of magnitude) ratio between the inhomogeneous and homogeneous broadening of Pr3+ : Y2SiO5. Slow-light effects due to the strong dispersion created by the spectral filter improved the suppression of the filter by also utilizing the time domain. As an application, we detected weak diffuse light shifted by ultrasound from the carrier about 2 MHz, after a 9 cm thick biological tissue. The coupling between light and matter is directly related to the relative direction of the light polarization and transition dipole moment of atoms. I developed a simulation program that was able to investigate the polarization direction and ellipticity of polarization of optical radiation propagating through the crystal. This might open up new opportunities for the investigation of interesting physics regarding propagation effects and for the improvement of spectral engineering of RE ions in the future. In order to deal with the sharp homogeneous transitions of the RE ions, the frequency of our dye laser was stabilized against a highly stabilized Fabry-Perot cavity using the Pound-Drever-Hall locking scheme.
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| 5. |
- Sabooni, Mahmood, et al.
(författare)
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Efficient Quantum Memory Using a Weakly Absorbing Sample
- 2013
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Ingår i: Physical Review Letters. - 1079-7114. ; 110:13
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Tidskriftsartikel (refereegranskat)abstract
- A light-storage experiment with a total (storage and retrieval) efficiency eta = 56% is carried out by enclosing a sample, with a single-pass absorption of 10%, in an impedance-matched cavity. The experiment is carried out using the atomic frequency comb (AFC) technique in a praseodymium-doped crystal (0: 05% Pr3+: Y2SiO5) and the cavity is created by depositing reflection coatings directly onto the crystal surfaces. The AFC technique has previously by far demonstrated the highest multimode capacity of all quantum memory concepts tested experimentally. We claim that the present work shows that it is realistic to create efficient, on-demand, long storage time AFC memories. DOI: 10.1103/PhysRevLett.110.133604
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| 6. |
- Sabooni, Mahmood, et al.
(författare)
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Spectral Engineering of Slow Light, Cavity Line Narrowing, and Pulse Compression
- 2013
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Ingår i: Physical Review Letters. - 1079-7114. ; 111:18
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Tidskriftsartikel (refereegranskat)abstract
- More than 4 orders of magnitude of cavity-linewidth narrowing in a rare-earth-ion-doped crystal cavity, emanating from strong intracavity dispersion caused by off-resonant interaction with dopant ions, is demonstrated. The dispersion profiles are engineered using optical pumping techniques creating significant semipermanent but reprogrammable changes of the rare-earth absorption profiles. Several cavity modes are shown within the spectral transmission window. Several possible applications of this phenomenon are discussed.
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| 7. |
- Sabooni, Mahmood, et al.
(författare)
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Storage and Recall of Weak Coherent Optical Pulses with an Efficiency of 25%
- 2010
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Ingår i: Physical Review Letters. - 1079-7114. ; 105:6
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate experimentally an efficient coherent rephasing scheme for the storage and recall of weak coherent light pulses in an inhomogeneously broadened optical transition in a Pr3+: YSO crystal at 2.1 K. Precise optical pumping using a frequency stable (approximate to 1 kHz linewidth) laser is employed to create a highly controllable atomic frequency comb structure. We report single photon level storage and retrieval efficiencies of 25%, based on coherent photon-echo-type reemission in the forward direction. The high efficiency is mainly a product of our highly controllable and precise ensemble-shaping technique. The coherence property of the quantum memory is proved through interference between a super-Gaussian pulse and the emitted echo.
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| 8. |
- Sabooni, Mahmood, et al.
(författare)
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Wave propagation in birefringent materials with off-axis absorption or gain
- 2016
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 93:1
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Tidskriftsartikel (refereegranskat)abstract
- The polarization direction of an electromagnetic field changes and eventually reaches a steady state when propagating through a birefringent material with off-axis absorption or gain. The steady state orientation direction depends on the magnitude of the absorption (gain) and the phase retardation rate. The change in the polarization direction is experimentally demonstrated in weakly doped (0.05%) Pr3+ : Y2SiO5 crystals, where the light polarization, if initially aligned along the most strongly absorbing principal axis, gradually switches to a much less absorbing polarization state during the propagation. This means that the absorption coefficient a in birefringent materials generally varies with length. This is important for, e.g., laser crystal gain media, highly absorbing and narrow band spectral filters and quantum memories.
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| 9. |
- Zhang, Huiliang, et al.
(författare)
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Slow light for deep tissue imaging with ultrasound modulation
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:13
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Tidskriftsartikel (refereegranskat)abstract
- Slow light has been extensively studied for applications ranging from optical delay lines to single photon quantum storage. Here, we show that the time delay of slow-light significantly improves the performance of the narrowband spectral filters needed to optically detect ultrasound from deep inside highly scattering tissue. We demonstrate this capability with a 9 cm thick tissue phantom, having 10 cm(-1) reduced scattering coefficient, and achieve an unprecedented background-free signal. Based on the data, we project real time imaging at video rates in even thicker phantoms and possibly deep enough into real tissue for clinical applications like early cancer detection. VC 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3696307]
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