Prasanna Srinivasan

Fabrication and operation of a two-dimensional ion-trap lattice on a high-voltage microchip

Microfabricated ion traps are a major advancement towards scalable quantum computing with trapped ions. The development of more versatile ion-trap designs, in which tailored arrays of ions are positioned in two dimensions above a microfabricated surface, will lead to applications in fields as varied as quantum simulation, metrology and atom-ion interactions. Current surface ion traps often have low trap depths and high heating rates, because of the size of the voltages that can be applied to them, limiting the fidelity of quantum gates. Here we report on a fabrication process that allows for the application of very high voltages to microfabricated devices in general and use this advance to fabricate a two-dimensional ion-trap lattice on a microchip. Our microfabricated architecture allows for reliable trapping of two-dimensional ion lattices, long ion lifetimes, rudimentary shuttling between lattice sites and the ability to deterministically introduce defects into the ion lattice.Microfabricated ion traps are a major advancement towards scalable quantum computing with trapped ions. The development of more flexible ion trap designs, in which tailored arrays of ions are positioned in two dimensions above a microfabricated surface, would lead to applications in fields as varied as quantum simulation, metrology and atom-ion interactions. Current surface ion traps often have low trap depths and high heating rates, due to the size of the voltages that can be applied to them, limiting the fidelity of quantum gates. In this article we report on a fabrication process that allows for the application of very high voltages to microfabricated devices in general and we apply this advance to fabricate a 2D ion trap lattice on a microchip. Our scalable microfabricated architecture allows for reliable trapping of 2D ion lattices, long ion lifetimes due to the deep trapping potential, rudimentary shuttling between lattice sites and the ability to deterministically introduce defects into the ion lattice.

Effect of Heat Transfer on Materials Selection for Bimaterial Electrothermal Actuators

Bimaterial electrothermal actuation is a commonly employed actuation method in microsystems. This paper focuses on optimal materials selection for bimaterial structures to maximize the thermomechanical response based on electrothermal heat-transfer analysis. Competition between different modes of heat transfer in electrothermally actuated cantilever bimaterial is analyzed for structures at the microscale (10 mum les L les1 mm) using a lumped heat-capacity formulation. The choice of materials has a strong influence on the functional effectiveness and the actuation frequency even though the electromechanical efficiency is inherently small (~10-5). Frequencies on the order of ~100 Hz to 15 kHz can be obtained for bimaterial structures at small scales by varying either the operating temperature range or the rate of heat dissipation. It is found that engineering alloys/metals perform better than other classes of materials for high-work high-frequency (~10 kHz) actuation within achievable temperature limits.

Atom chip for BEC interferometry

We have fabricated and tested an atom chip that operates as a matter wave interferometer. In this communication we describe the fabrication of the chip by ion-beam milling of gold evaporated onto a silicon substrate. We present data on the quality of the wires, on the current density that can be reached in the wires and on the smoothness of the magnetic traps that are formed. We demonstrate the operation of the interferometer, showing that we can coherently split and recombine a Bose–Einstein condensate with good phase stability.

Optimal Materials Selection for Bimaterial Piezoelectric Microactuators

Piezoelectric actuation is one of the commonly employed actuation schemes in microsystems. This paper focuses on identifying and ranking promising active material/substrate combinations for bimaterial piezoelectric (BPE) microactuators based on their performance. The mechanics of BPE structures following simple beam theory assumptions available in the literature are applied to evolve critical performance metrics which govern the materials selection process. Contours of equal performance are plotted in the domain of the governing piezoelectric material properties (coefficients, elastic modulus, coupling factors and dielectric constants) for commonly employed substrates to identify optimal material combinations for various functional requirements. The influence of materials selection on the actuation efficiency, quality factor and the electromechanical impedance is also discussed. Selection of a suitable actuation mechanism for a boundary layer flow control application is illustrated by comparing the performance limits of BPE and bimaterial electrothermal actuators considering the constraints on the functional requirements imposed by the associated microfabrication routes.

Material Selection for Optimal Design of Thermally Actuated Pneumatic and Phase Change Microactuators

This paper discusses a methodology to select materials which deliver the best performance for thermally actuated pneumatic and phase change microactuators. The material selection is based on performance metrics estimated using simple closed form solutions for classical linear elastic theory for axisymmetric plates/membranes and lumped heat capacity thermal models. Although the elastic moduli of the diaphragm materials dictate the volume expansion for a given temperature rise, their influence on the achievable pressure difference is much less. It is found that engineering polymers are most suitable for thermopneumatically actuated diaphragms for delivering large displacements and work for the achievable pressures at frequencies of a few hundreds of Hertz. The membrane stresses due to in-plane pre-tension are found to have an adverse effect on the actuator performance. The material issues which constrain the performance limits of phase change actuators are also assessed, and the promising characteristics of paraffin waxes for microsystem applications are discussed.

Modeling of Thermally Driven Resonance at Multiscales

Understanding the mechanisms of thermally driven resonance is a key for designing many engineering and physical systems especially at small scales. This paper focuses on the modeling aspects of such phenomena using the classical Fourier diffusion theory. Critical analysis revealed that the thermally induced resonant excitation is characterized by the generation of multiple wave trains with a constant phase shift as opposed to the single standing wave generated in a mechanically driven resonant response. The hypothesis proposed herein, underpin a broad range of scientific and technological developments and the analytical treatment enables design of thermally driven resonant systems with improved performance

Microfabricated two-dimensional (2D) hexagonal lattice trap

We present the design, fabrication and experimental result of a two-dimensional (2D) hexagonal lattice trap capable of trapping a lattice of charged particles. The microtrap consists of 29-hexagonal lattice sites each capable of trapping an ion. Each trapped ion has up to six neighbors with an ion-ion separation of 270.5 μm. A SOI-based structure was optimized to improve the trap performance substantially increasing the breakdown voltage (>1 kV) previously reported. Ytterbium (174Yb002B;) ions were successfully confined in an ultra-high vacuum (UHV) system by applying a radio frequency (RF) voltage of 455 V at a drive frequency Ω/2π = 32.2 MHz. In addition, our design is suitable to control the trapping height in situ by applying a secondary rf potentials. Numerical simulations of the 2D lattice trap demonstrated a large operating range by trapping ions as well as micro-particles with charge to mass ratio in order of 10-4 to 105 Kg/C at a frequency range of a few kilohertz to megahertz.