Rory Speirs

The University of Maryland · Joint Quantum Institute

Control of Coulomb expansion in charged particle beams is of critical importance for applications including electron and ion microscopy, injectors for particle accelerators and in ultrafast electron diffraction, where space-charge effects constrain the temporal and spatial imaging resolution. The development of techniques to reverse space-charge-dr...

We present a pressure sensor based on a Michelson interferometer, for use in photoacoustic tomography. Quadrature phase detection is employed allowing measurement at any point on the mirror surface without having to retune the interferometer, as is typically required by Fabry-Perot type detectors. This opens the door to rapid full surface detection...

Cold atom electron and ion sources produce electron bunches and ion beams by photoionization of laser-cooled atoms. They offer high coherence and the potential for high brightness, with applications including ultra-fast electron-diffractive imaging of dynamic processes at the nanoscale. The effective brightness of electron sources has been limited...

We investigate the effect of 2-beam coupling in different imaging geometries in generating intensity-difference squeezing from four-wave mixing (4WM) in Rb atomic vapors. A recently-introduced dual-seeding technique can cancel out the classical noise in a seeded four-wave mixing process. This dual-seeding technique, however, can introduce new compl...

We investigate the effect of 2-beam coupling in different imaging geometries in generating intensity-difference squeezing from four-wave mixing (4WM) in Rb atomic vapors. A recently-introduced dual-seeding technique can cancel out the classical noise in a seeded four-wave mixing process. This dual-seeding technique, however, can introduce new compl...

We study the effect of homodyne detector visibility on the measurement of quadrature squeezing for a spatially multi-mode source of two-mode squeezed light. Sources like optical parametric oscillators (OPO) typically produce squeezing in a single spatial mode because the nonlinear medium is within a mode-selective optical cavity. For such a source,...

We study the effect of homodyne detector visibility on the measurement of quadrature squeezing for a spatially multi-mode source of two-mode squeezed light. Sources like optical parametric oscillators (OPO) typically produce squeezing in a single spatial mode because the nonlinear medium is within a mode-selective optical cavity. For such a source,...

We demonstrated sub-10 Hz intensity-difference squeezing and eliminate 2-beam coupling effects in quantum correlated images formed using four-wave mixing. With these techniques, we are closer to taking pixel-by-pixel quantum images with a CCD camera.

We report the generation of strong, bright-beam intensity-difference squeezing down to measurement frequencies below 10 Hz. We generate two-mode squeezing in a four-wave mixing (4WM) process in Rb vapor, where the single-pass-gain nonlinear process does not require cavity locking and only relies on passive stability. We use diode laser technology a...

We have obtained broadband intensity-difference squeezing from sub 10 Hz to 20 MHz via four-wave mixing (4WM) in a rubidium vapor. This was accomplished by dual-seeding the 4WM process and using semiconductor diode lasers.

We present a method for using bright beams of intensity difference squeezed light to perform sub-shot-noise imaging. The intensity correlated twin beams are generated by four wave mixing in rubidium vapour.

We introduce a dual-seeding technique to cancel out the classical noise in a seeded four-wave mixing process. Two-beam coupling in the process can degrade quantum images. Seeding with skew rays can avoid the problem.

We report the generation of strong, bright-beam intensity-difference squeezing down to measurement frequencies below 10 Hz. We generate two-mode squeezing in a four-wave mixing (4WM) process in Rb vapor, where the single-pass-gain nonlinear process does not require cavity locking and only relies on passive stability. We use diode laser technology a...

We demonstrate a method for the deterministic production of single ions by exploiting the correlation between an electron and associated ion following ionization. Coincident detection and feedback in combination with Coulomb-driven particle selection allows for high-fidelity heralding of ions at a high repetition rate. Extension of the scheme beyon...

Brightness is a key figure of merit for charged particle beams, and time-resolved brightness measurements can elucidate the processes involved in beam creation and manipulation. Here we report on a simple, robust, and widely applicable method for the measurement of beam brightness with temporal resolution by streaking one-dimensional pepperpots, an...

We have obtained bright-beam intensity-difference squeezing below 10 Hz via four-wave mixing in a rubidium vapor. This was accomplished by increasing phase matching angle and using two seed beams to balance the power.

We present an ionization mechanism for use in a cold atom electron source with the goal of producing highly monochromatic electron beams. We experimentally produce a map of the Stark states of Rb85 below the ionization threshold and identify states that undergo selective field ionization. The properties of an electron beam produced by field-assiste...

We make direct measurements of the duration of ultrafast cold-electron bunches produced by photoionization of laser-cooled atoms. We show that the bunch duration can vary by up to six orders of magnitude for relatively small changes in laser wavelength that enhance or inhibit specific photoexcitation pathways and below-threshold tunneling. By selec...

We demonstrate precise control of charged particle bunch shape with a cold atom electron and ion source to create bunches with linear and, therefore, reversible Coulomb expansion. Using ultracold charged particles enables detailed observation of space-charge effects without loss of information from thermal diffusion, unambiguously demonstrating tha...

Coffee is prepared by the extraction of a complex array of organic molecules from the roasted bean, which has been ground into fine particulates. The extraction depends on temperature, water chemistry and also the accessible surface area of the coffee. Here we investigate whether variations in the production processes of single origin coffee beans...

We implement high-efficiency coherent excitation to a Rydberg state using stimulated Raman adiabatic passage in a cold atom electron and ion source, achieving a peak efficiency of 85%, a 1.7 times improvement relative to incoherent pulsed-laser excitation. Using pulsed electric field ionization of the Rydberg atoms we created electron bunches with...

Cold atom electron sources are a promising alternative to traditional photocathode sources for use in ultrafast electron diffraction due to greatly reduced electron temperature at creation, and the potential for a corresponding increase in brightness. Here we demonstrate single-shot, nanosecond electron diffraction from monocrystalline gold using c...

We create ultracold ion bunches via precisely shaped photoionisation of laser cooled atoms that exhibit linear Coulomb self-field expansion, smaller emittance growth and hence improved brightness under transverse focusing in comparison to standard Gaussian bunches.

We present single-shot nanosecond and picosecond electron diffraction measurements from gold and graphene using ultracold electrons generated by photoionisation of laser cooled atoms.