Qudsia Quraishi

National Institute of Standards and Technology, GAI, Maryland, United States

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Publications (38)76.22 Total impact

  • Daniel T. Stack, Patricia J. Lee, Qudsia Quraishi
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    ABSTRACT: The ability to filter unwanted light signals is critical to the operation of quantum memories based on neutral atom ensembles. Here we demonstrate an efficient frequency filter which uses a vapor cell filled with 85Rb and a buffer gas to attenuate both residual laser light and noise photons by nearly two orders of magnitude with little loss to the single photons associated with our cold 87Rb quantum memory. This simple, passive filter provides an additional 18 dB attenuation of our pump laser and erroneous spontaneous emissions for every 1 dB loss of the single photon signal. We show that the addition of a frequency filter increases the non-classical correlations and the retrieval efficiency of our quantum memory by ≈ 35%.
    Optics Express 03/2015; 23(5). DOI:10.1364/OE.23.006822 · 3.53 Impact Factor
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    Dan T. Stack, Patricia J. Lee, Qudsia Quraishi
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    ABSTRACT: The ability to filter unwanted light signals is critical to the operation of quantum memories based on neutral atom ensembles. Here we demonstrate an efficient frequency filter which uses a vapor cell filled with $^{85}$Rb and a buffer gas to attenuate both residual laser light and noise photons by nearly two orders of magnitude with little loss to the single photons associated with our cold $^{87}$Rb quantum memory. This simple, passive filter provides an additional 18 dB attenuation of our pump laser and erroneous spontaneous emissions for every 1 dB loss of the single photon signal. We show that the addition of a frequency filter increases the non-classical correlations and readout efficiency of our quantum memory by $\approx35\%$.
  • Daniel Stack, Patricia J. Lee, Qudsia Quraishi
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    ABSTRACT: Quantum networks provide conduits capable of transmitting quantum information that connect to nodes at remote locations where the quantum information can be stored or processed. Fiber-based transmission of quantum information over long distances may be achieved using quantum memory elements and quantum repeater protocols. However, atombased quantum memories typically involve interactions with light fields outside the telecom window needed to minimize absorption in transmission by optical fibers. We report on progress towards a quantum memory based on the generation of 795 nm spontaneously emitted single photons by a write-laser beam interacting with a cold 87Rb ensemble. The single photons are then frequency-converted into (out of) the telecomm band via difference (sum) frequency generation in a PPLN crystal. Finally, the atomic state is read out via the interaction of a read-pulse with the quantum memory. With such a system, it will be possible to realize a long-lived quantum memory that will allow transmission of quantum information over many kilometers with high fidelity, essential for a scalable, long-distance quantum network.
    SPIE Sensing Technology + Applications; 05/2014
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    Qudsia Quraishi, Scott A. Diddams, Leo Hollberg
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    ABSTRACT: Stabilized optical frequency combs (OFC) can have remarkable levels of coherence across their broad spectral bandwidth. We study the scaling of the optical noise across hundreds of nanometers of optical spectra. We measure the residual phase noise between two OFC's (having offset frequencies $f^{(1)}_0 $ and $f^{(2)}_0$) referenced to a common cavity-stabilized narrow linewidth CW laser. Their relative offset frequency $ \Delta f_0 = f^{(2)}_0 - f^{(1)}_0 $, which appears across their entire spectra, provides a convenient measure of the phase noise. By comparing $\Delta f_0$ at different spectral regions, we demonstrate that the observed scaling of the residual phase noise is in very good agreement with the noise predicted from the standard frequency comb equation.
    Optics Communications 01/2014; 320. DOI:10.1016/j.optcom.2014.01.030 · 1.54 Impact Factor
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    ABSTRACT: We stabilize a chosen radiofrequency beat note between two optical fields derived from the same mode-locked laser pulse train, in order to coherently manipulate quantum information. This scheme does not require access or active stabilization of the laser repetition rate. We implement and characterize this external lock, in the context of two-photon stimulated Raman transitions between the hyperfine ground states of trapped 171-Yb+ quantum bits.
    Optics Letters 12/2013; 39(11). DOI:10.1364/OL.39.003238 · 3.18 Impact Factor
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    ABSTRACT: Fiber-based transmission of quantum information over long distances may be achieved using quantum memory elements and quantum repeater protocols.footnotetextDuan et al., Nature 414, 413-418 (2001) However, atom-based quantum memories typically involve interactions with light fields outside the telecom window where attenuation in optical fibers is at a minimum. We report on progress towards a quantum memory based on the generation of 780 nm spontaneously emitted single photons by an off-resonant Raman beam interacting with a cold ^87Rb ensemble. The single photons are then frequency converted into telecom photons (via four-wave mixing in a cold Rb sample), sent through a 13 km fiber, and then converted back to 780 nm photons (via sum frequency generation in a PPLN crystal). Finally, the atomic state is read out via the interaction of another off-resonant Raman beam with the quantum memory. With such a system it will be possible to realize a long-lived quantum memory that will allow transmission of quantum information over many kilometers with high fidelity, essential for a scalable, long-distance quantum network.
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    ABSTRACT: Enabling secure communication, unparalleled computing capabilities, and fundamental nonlocality physics exploration, the development of quantum repeaters is the key quantum information processing technology advance needed for implementing real world quantum networks beyond the laboratory environment. Currently, components exist for intra-laboratory quantum networks but no system exists for connecting distant ( 1 km ) quantum memories in the real world. We present a physics analysis of quantum repeater network designs for intracity optical fiber connections between nodes based on atomic memories and linear optics. Long distances will necessitate the use of (1) two-photon Hong-Ou-Mandel style interference between atomic ensembles for entanglement swapping, and (2) photonic qubit wavelength conversion between atomic emissions and photons at telecommunication wavelengths in fiber. We report on our experimental progress towards implementing A Quantum Network with Atoms and Photons (QNET-AP), a quantum repeater network test-bed, between the US Army Research Laboratory (ARL) and the Joint Quantum Institute (JQI) of the National Institute of Standards and Technology (NIST) and the University of Maryland (UMD).
    Proceedings of SPIE - The International Society for Optical Engineering 10/2012; DOI:10.1117/12.974144 · 0.20 Impact Factor
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    ABSTRACT: We demonstrate a simple pulse shaping technique designed to improve the fidelity of spin-dependent force operations commonly used to implement entangling gates in trapped ion systems. This extension of the Mølmer-Sørensen gate can theoretically suppress the effects of certain frequency and timing errors to any desired order and is demonstrated through Walsh modulation of a two qubit entangling gate on trapped atomic ions. The technique is applicable to any system of qubits coupled through collective harmonic oscillator modes.
    Physical Review Letters 07/2012; 109(2):020503. DOI:10.1103/PhysRevLett.109.020503 · 7.73 Impact Factor
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    ABSTRACT: Optical frequency combs, emitted by ultrafast modelocked pulsed lasers, are excellent tools to perform quantum coherent control. The spectral purity, large bandwidth and high pulse powers makes these sources attractive for precision control of multi-level atoms. We envisage using pairs of OFC modes to drive stimulated Raman transitions between the two hyperfine clock states of ^87Rb confined on an atom chip. The Raman transitions will be driven using an all optical, four photon technique, whereby the first photon pair drives off-resonantly to the intermediate state ^2S1/2 |F=2, mf=0> and then a second photon pair resonantly drives to ^2S1/2 |F=2, mf=+1>. Co-propagating Raman fields impart only a spin flip whereas non-copropagating fields transfer two photon recoil momentum to the atoms, thus entangling the internal spin with the external motion of the atoms. For site dependent control, we plan to use the high AC Stark shifts produced by the high intensity pulses.
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    ABSTRACT: A technique to drive stimulated Raman transition between spin and/or momentum states of ultracold 87Rb atoms confined on an atomchip trap is discussed. We present our experimental and theoretical approach to an all-optical manipulation of the atoms using an optical frequency comb emitted by a modelocked ultrafast pulsed laser.
    Proceedings of SPIE - The International Society for Optical Engineering 05/2012; DOI:10.1117/12.918944 · 0.20 Impact Factor
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    ABSTRACT: A technique to drive stimulated optical Raman transitions between spin and/or momentum states of ultracold 87Rb atoms in a waveguide micro chip trap is discussed.
    Lasers and Electro-Optics (CLEO), 2012 Conference on; 01/2012
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    ABSTRACT: Trapped ions entangled via photonic interactions are promising avenues for quan-tum information processing. Here, we report advances towards combining photonic gates be-tween distant ions with Coulombic gates between nearby ions to demonstrate scalable quantum networks.
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    ABSTRACT: Control of spin dependent forces is important for generating entanglement and realizing quantum simulations in trapped ion systems. Here we propose and implement a composite pulse sequence based on the Molmer-Sorenson gate to decrease gate infidelity due to frequency and timing errors. The composite pulse sequence uses an optical frequency comb to drive Raman transitions simultaneously detuned from trapped ion transverse motional red and blue sideband frequencies. The spin dependent force displaces the ions in phase space, and the resulting spin-dependent geometric phase depends on the detuning. Voltage noise on the rf electrodes changes the detuning between the trapped ions' motional frequency and the laser, decreasing the fidelity of the gate. The composite pulse sequence consists of successive pulse trains from counter- propagating frequency combs with phase control of the microwave beatnote of the lasers to passively suppress detuning errors. We present the theory and experimental data with one and two ions where a gate is performed with a composite pulse sequence. This work supported by the U.S. ARO, IARPA, the DARPA OLE program, the MURI program; the NSF PIF Program; the NSF Physics Frontier Center at JQI; the European Commission AQUTE program; and the IC postdoc program administered by the NGA.
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    ABSTRACT: Optical frequency combs (OFCs), emitted by ultrafast modelocked pulsed lasers, are excellent tools to perform quantum coherent control. The spectral purity, large bandwidth and high pulse powers makes these sources attractive for precision control of multi-level atoms. Recent experiments have shown that an OFC can be used to coherently control and entangle trapped ion qubits by means of off-resonant Raman transitions [1]. Here, we propose to extend this technique to neutral atoms confined on an atom chip and we also propose to implement an all-optical technique for hyperfine qubit manipulation using OFCs. We envisage using pairs of OFC modes to drive stimulated Raman transitions between the two hyperfine clock states of 87Rb confined on an atom chip. The Raman transitions will be driven using a four photon technique whereby the first photon pair drives off-resonantly to the intermediate state 2S1/2 |F=2, mf=0> and then a second photon pair resonantly drives to 2S1/2 |F=2, mf=+1>. Co-propagating Raman fields impart only a spin flip whereas non-copropagating fields transfer two photon recoil momentum to the atoms, thus entangling the internal spin with the external motion of the atoms. We plan on using the frequency comb to impart state dependent forces to the atomic cloud.
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    ABSTRACT: Quantum information processing with trapped ions has traditionally involved state preparation, manipulation (eg. quantum gates) and detection using CW lasers. Quantum gates implemented with ions typically involve optical Raman transitions between two atomic levels. An optical frequency comb, emitted by a pulsed laser, is an excellent tool for bridging atomic frequency differences. Previously, we demonstrated quantum gates and separately, ultrafast spin manipulation, using pulsed lasers [1,2]. Unlike the CW case, employing pulsed lasers has the marked advantage of both low spontaneous emission and low AC Stark shifts, because the high powers available from pulsed lasers allow for larger detunings from optical resonance. Here, we show both experimentally and theoretically the scaling of the differential Stark shift with detuning (6 THz to 20 THz) of the Raman fields, achieving values of 10-3 of the Rabi frequency. [1] D. Hayes, et al., Phys. Rev. Lett. 104, 140501 (2010) [2] W. C. Campbell, et al., Phys. Rev. Lett. 105, 090502 (2010). *Currently NRC postdoc with SEDD, ARL, Adelphi, MD. Support: DARPA OLE under ARO contract, IARPA under ARO contract, NSF PIF Program, NSF PFC at JQI and *IC Postdoc administered by the NGA.
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    ABSTRACT: We demonstrate single-qubit operations on a trapped atom hyperfine qubit using a single ultrafast pulse from a mode-locked laser. We shape the pulse from the laser and perform a π rotation of the qubit in less than 50 ps with a population transfer exceeding 99% and negligible effects from spontaneous emission or ac Stark shifts. The gate time is significantly shorter than the period of atomic motion in the trap (Ω(Rabi)/ν(trap)>10(4)), demonstrating that this interaction takes place deep within the strong excitation regime.
    Physical Review Letters 08/2010; 105(9):090502. DOI:10.1103/PhysRevLett.105.090502 · 7.73 Impact Factor
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    ABSTRACT: We demonstrate the use of an optical frequency comb to coherently control and entangle atomic qubits. A train of off-resonant ultrafast laser pulses is used to efficiently and coherently transfer population between electronic and vibrational states of trapped atomic ions and implement an entangling quantum logic gate with high fidelity. This technique can be extended to the high field regime where operations can be performed faster than the trap frequency. This general approach can be applied to more complex quantum systems, such as large collections of interacting atoms or molecules.
    Physical Review Letters 04/2010; 104(14):140501. DOI:10.1103/PhysRevLett.104.140501 · 7.73 Impact Factor
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    ABSTRACT: The spectral purity and large bandwidth of pulsed lasers makes them attractive candidates for precision control of multi-level atomic systems. We use a train of off resonant picosecond pulses from a mode-locked laser to drive stimulated Raman transitions between the hyperfine levels (˜10 GHz spacing) of trapped ytterbium ions and to cool to the quantum ground state of motion. By simultaneously addressing the spin and the motion of trapped ions using a train of laser pulses, we apply spin-dependent forces to create a single-ion Schrodinger cat state and implement a gate between two trapped ions to entangle their spins [1]. We also use high-intensity pulses to demonstrate fast (
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    ABSTRACT: We describe an experiment to achieve ultrafast qubit operations on trapped <sup>171</sup>Yb<sup>+</sup> ions. We plan to use a series of short optical pulses to perform bit rotations and multi-bit entangling gates independent of ion temperature.
    Lasers and Electro-Optics, 2009 and 2009 Conference on Quantum electronics and Laser Science Conference. CLEO/QELS 2009. Conference on; 07/2009
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    ABSTRACT: Ultrashort light pulses are an attractive tool for trapped ion quantum information processing. High pulse intensity permits far-detuned (>10 nm) operation, where decoherence from differential AC Stark shifts and spontaneous emission is suppressed. Short pulse duration allows interaction times shorter than a trap oscillation, circumventing the need for cooling to the Lamb-Dicke limit. We describe an experiment with trapped ^171Yb^+ using a vanadate laser (˜10 ps pulses at 355 nm). Since the single pulse bandwidth exceeds the S1/2 hyperfine splitting, coherent Raman transitions between qubit states should be possible. This is in contrast to our previous work [1] with near-resonant pulses that coherently transfer population to the P-state. It should also be possible to use a series of multiple pulses to impart spin-dependent forces. By controlling the pulse timing and phase we could then entangle multiple ions in a temperature insensitive manner [2,3]. [1] Madsen et al., PRL 97, 040505 (2006). [2] Garc'ia-Ripoll et al., PRL 91, 157901 (2003). [3] Duan, PRL 93, 100502 (2004).

Publication Stats

236 Citations
76.22 Total Impact Points

Institutions

  • 2005–2013
    • National Institute of Standards and Technology
      • Time and Frequency Division
      GAI, Maryland, United States
  • 2012
    • Loyola University Maryland
      • Department of Physics
      Baltimore, Maryland, United States
  • 2009
    • University of Maryland, College Park
      • Department of Physics
      College Park, MD, United States