Papers by Silvia Bergamini
Photonics
We analyze schemes of high-fidelity multi-qubit CNOTN and C2NOT2 gates for alkali metal neutral a... more We analyze schemes of high-fidelity multi-qubit CNOTN and C2NOT2 gates for alkali metal neutral atoms used as qubits. These schemes are based on the electromagnetically induced transparency and Rydberg blockade. The fidelity of homonuclear multi-qubit CNOTN gate based on Rydberg blockade was limited by the undesirable interaction between the target atoms and by the coupling laser intensity. We propose overcoming these limits by using strong heteronuclear dipole–dipole interactions via Förster resonances for control and target atoms, while the target atoms are coupled by a weaker van der Waals interaction. We optimized the gate performance in order to achieve higher fidelity, while keeping the coupling laser intensity as small as possible in order to improve the experimental feasibility of the gate schemes. We also considered the optimization of the schemes of the C2NOT2 gates, where the fidelity is affected by the relation between the control–control, control–target and target–targe...
Proceeding of Progress in Plasma Processing of Materials, 2003, 2003
Physical Review A, 2016
We analyze the operation of a novel sensor based on atom interferometry, which can achieve supra-... more We analyze the operation of a novel sensor based on atom interferometry, which can achieve supra-classical sensitivity by exploiting quantum correlations in mixed states of many qubits. The interferometer is based on quantum gates which use coherently-controlled Rydberg interactions between a single atom (which acts as a control qubit) and an atomic ensemble (which provides register qubits). In principle, our scheme can achieve precision scaling with the size of the ensemble-which can extend to large numbers of atoms-while using only single-qubit operations on the control and bulk operations on the ensemble. We investigate realistic implementation of the interferometer, and our main aim is to develop a new approach to quantum metrology that can achieve quantum-enhanced measurement precision by exploiting coherent operations on large impure quantum states. We propose an experiment to demonstrate the enhanced sensitivity of the protocol, and to investigate a transition from classical to supra-classical sensitivity which occurs when using highly-mixed probe states.
New Journal of Physics, 2014
View the article online for updates and enhancements. Related content Simulated quantum process t... more View the article online for updates and enhancements. Related content Simulated quantum process tomography of quantum gates with Rydberg superatoms I I Beterov, M Saffman, E A Yakshina et al.-Quantum computing with atomic qubits and Rydberg interactions: Progress and challenges M Saffman-Quantum information processing with superconducting circuits: a review G Wendin-Recent citations Creating and probing the Sachdev-Ye-Kitaev model with ultracold gases: Towards experimental studies of quantum gravity Ippei Danshita et al-Quantum-enhanced protocols with mixed states using cold atoms in dipole traps K Krzyzanowska et al-Supraclassical measurement using singleatom control of an atomic ensemble Calum MacCormick et al
Plasma harmonic lissajous measurements
We report the design and construction of a non-invasive radio frequency instrument used for real-... more We report the design and construction of a non-invasive radio frequency instrument used for real-time measurement of plasma-generated harmonics of the fundamental drive frequency of 13.56 MHz. The design allows the selection of a single harmonic for analysis. A digital oscilloscope is employed to display one harmonic (n = 4 to 7) with respect to the fundamental as a Lissajous figure. The instrument achieves very high sensitivity in process discrimination by utilizing an amplifier with very low noise-figure (NF=2dB), by rejecting spurious FM broadcast and co-channel signals and by tuning to the plasma and plasma-tool frequency response to changes in plasma state. Information about the amplitude and relative phase of the two signals can be readily extracted, permitting the identification and classification of a unique plasma state as a real-time evolving 2-dimensional signature. This can be used to calibrate the plasma as a function of pump-down time, pressure and radio frequency powe...
Manipulating individual atoms in microscopic optical dipole traps
Postconference Digest Quantum Electronics and Laser Science, 2003. QELS., 2003
ABSTRACT We have realized very small optical dipole traps to store and manipulate individual atom... more ABSTRACT We have realized very small optical dipole traps to store and manipulate individual atoms. Due to the small trap volume, a "collisional blockade" mechanism limits the number of trapped atoms to 1 over a large range of loading rates. We have studied this collisional blockade effect, and measured the oscillation frequencies and temperature of a single trapped atom, that appears to be in the sub-Doppler regime. Various mechanisms for turner cooling will be described, as well as the perspectives for using this system for quantum information processing.
Laser Spectroscopy, 2005
We present recent results on the coherent control of an optical transition in a single rubidium a... more We present recent results on the coherent control of an optical transition in a single rubidium atom, trapped in an optical tweezer. We excite the atom using resonant light pulses that are short (4 ns) compared with the lifetime of the excited state (26 ns). By varying the intensity of the laser pulses, we can observe an adjustable number of Rabi oscillations, followed by free decay once the light is switched off. To generate the pulses we have developed a novel laser system based on frequency doubling a telecoms laser diode at 1560 nm. By setting the laser intensity to make a π pulse, we use this coherent control to make a high quality triggered source of single photons. We obtain an average single photon rate of 9600 s −1 at the detector. Measurements of the second-order temporal correlation function show almost perfect antibunching at zero delay. In addition, we present preliminary results on the use of Raman transitions to couple the two hyperfine levels of the ground state of our trapped atom. This will allow us to prepare and control a qubit formed by two hyperfine sub-levels.
Science, 2005
By illuminating an individual rubidium atom stored in a tight optical tweezer with short resonant... more By illuminating an individual rubidium atom stored in a tight optical tweezer with short resonant light pulses, we created an efficient triggered source of single photons with a well-defined polarization. The measured intensity correlation of the emitted light pulses exhibits almost perfect antibunching. Such a source of high-rate, fully controlled single-photon pulses has many potential applications for quantum information processing.
A moving-mirror frequency modulator for cold atom spectroscopy
Review of Scientific Instruments, 2002
We have investigated the use of a moving or “Doppler” mirror to probe laser cooled atoms. The dev... more We have investigated the use of a moving or “Doppler” mirror to probe laser cooled atoms. The device uses the Doppler shift induced on reflection at a moving surface to modulate the frequency of a probing laser beam, with a modulation bandwidth and frequency resolution sufficient for the narrow spectral features typically encountered. We anticipate that the device could be a simple and cost-effective alternative to acousto-optic modulators for cold atom spectroscopy, and demonstrate its usefulness by performing stimulated optical Compton scattering on an optical molasses.
Physical Review Letters, 2005
We demonstrate the phenomenon of resonant activation in a nonadiabatically driven dissipative opt... more We demonstrate the phenomenon of resonant activation in a nonadiabatically driven dissipative optical lattice with broken time symmetry. The resonant activation results in a resonance as a function of the driving frequency in the current of atoms through the periodic potential. We demonstrate that the resonance is produced by the interplay between deterministic driving and fluctuations, and we also show that by changing the frequency of the driving it is possible to control the direction of the diffusion.
Physical Review Letters, 2005
We analyze the atomic dynamics in an ac driven periodic optical potential which is symmetric in b... more We analyze the atomic dynamics in an ac driven periodic optical potential which is symmetric in both time and space. We experimentally demonstrate that in the presence of dissipation the symmetry is broken, and a current of atoms through the optical lattice is generated as a result.
Physical Review Letters, 2006
We demonstrated experimentally that the momentum distribution of cold atoms in dissipative optica... more We demonstrated experimentally that the momentum distribution of cold atoms in dissipative optical lattices is a Tsallis distribution. The parameters of the distribution can be continuously varied by changing the parameters of the optical potential. In particular, by changing the depth of the optical lattice, it is possible to change the momentum distribution from Gaussian, at deep potentials, to a power-law tail distribution at shallow optical potentials.
Journal of the Optical Society of America B, 2004
We have generated multiple micrometer-sized optical dipole traps for neutral atoms using holograp... more We have generated multiple micrometer-sized optical dipole traps for neutral atoms using holographic techniques with a programmable liquid-crystal spatial light modulator. The setup allows storing of a single atom per trap and addressing and manipulation of individual trapping sites.
New Journal of Physics, 2011
We present the direct measurements of electric-dipole moments for 5P 3/2 → nD 5/2 transitions wit... more We present the direct measurements of electric-dipole moments for 5P 3/2 → nD 5/2 transitions with 20 < n < 48 for Rubidium atoms. The measurements were performed in an ultracold sample via observation of the Autler-Townes splitting in a three-level ladder scheme, commonly used for 2-photon excitation of Rydberg states. To the best of our knowledge, this is the first systematic measurement of the electric dipole moments for transitions from low excited states of rubidium to Rydberg states. Due to its simplicity and versatility, this method can be easily extended to other transitions and other atomic species with little constraints. Good agreement of the experimental results with theory proves the reliability of the measurement method.
Journal de Physique IV (Proceedings), 2004
We present a brief overview of optical trapping experiments of individual neutral atoms. Then we ... more We present a brief overview of optical trapping experiments of individual neutral atoms. Then we describe in more details an experiment using a very small optical dipole trap, that is designed to store and manipulate individual atoms. Due to the very small dipole trap volume, a "collisional blockade" mechanism locks the average number of trapped atoms on the value 0.5 over a large range of loading rates. We study this regime experimentally, and we describe methods to measure the oscillation frequencies and the temperature of a single atom in the trap with a high accuracy.
Applied Physics B, 2005
We have constructed a pulsed laser system for the manipulation of cold 87 Rb atoms. The system co... more We have constructed a pulsed laser system for the manipulation of cold 87 Rb atoms. The system combines optical telecommunications components and frequency doubling to generate light at 780 nm. Using a fast, fibrecoupled intensity modulator, output from a continuous laser diode is sliced into pulses with a length between 1.3 and 6.1 ns and a repetition frequency of 5 MHz. These pulses are amplified using an erbium-doped fibre amplifier, and frequency-doubled in a periodically poled lithium niobate crystal, yielding a peak power up to 12 W. Using the resulting light at 780 nm, we demonstrate Rabi oscillations on the F = 2 ↔ F ′ = 3-transition of a single 87 Rb atom.
Remote-coupled Oxygen Plasma Harmonic Measurements for Process Monitoring
ABSTRACT About the book: This book presents state-of-the-art analysis of developments in plasma p... more ABSTRACT About the book: This book presents state-of-the-art analysis of developments in plasma physics.
Physical Review A, 2017
We present a blueprint for building a fault-tolerant universal quantum computer with Rydberg atom... more We present a blueprint for building a fault-tolerant universal quantum computer with Rydberg atoms. Our scheme, which is based on the surface code, uses individually-addressable opticallytrapped atoms as qubits and exploits electromagnetically induced transparency to perform the multi-qubit gates required for error correction and computation. We discuss the advantages and challenges of using Rydberg atoms to build such a quantum computer, and we perform error correction simulations to obtain an error threshold for our scheme. Our findings suggest that Rydberg atoms are a promising candidate for quantum computation, but gate fidelities need to improve before fault-tolerant universal quantum computation can be achieved.
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Papers by Silvia Bergamini