Novel photonic control architecture for atomic and ionic quantum computing

Over the past years, a second quantum revolution has emerged because researchers gained unprecedented control over nature’s best qubit, the atom. In atomic and ionic quantum computing, qubit gates are implemented with a set of laser beams that span from the UV to near-IR. These laser beams have to be modulated with speeds above 1 MHz (up to 100s of MHz to implement optimal qubit control pulses), with extreme light extinction ratios (above 50 dB to minimize gate errors), and without interfering background light (i.e. very clean laser beams without any sidelobes). In such systems, the problem is therefore not so much the qubit scaling, but the scaling of the photonic control system.

Photonic integrated circuits (PICs) are a promising route to integrate many optical functionalities with performance specs that surpass their bulk counterparts on a single chip, thereby providing scalability and cost reduction as additional advantages. Traditionally, most PICs were developed in silicon due to the dense integration possibilities and the fact that devices could be fabricated using technologies from the CMOS electronics world, allowing high-quality, and repeatable fabrication processes. Silicon is however not transparent for visible wavelengths and hence cannot be use for atomic and ionic control. Silicon nitride (SiN) on the other hand is transparent in the relevant wavelength range, but suffers from one major drawback: it is very hard to modulate the phase of the light signal in a fast and efficient way.

In addition to the difficulties of making efficient and fast phase-shifters, it is moreover important to note that the amplitude modulators and beam scanners using these phase shifters are having performance issues themselves. Amplitude modulators typically rely on interference to switch the light ON/OFF, so they are very sensitive to fabrication imperfections (e.g. waveguide roughness which leads to phase errors) and environmental perturbations (e.g. local temperature changes on the chip). As such there is always need for precise feedback control. In addition, interference-based amplitude modulators typically have low extinction ratios (about 20 dB), requiring a cascading to achieve 50 dB, which in turn will increase optical excess losses. Optical-phased arrays, commonly used for beam scanning, on the other hand suffer from the existence of sidelobes, creating unwanted background light and optical excess loss.

It is therefore clear that the traditional approaches commonly used in integrated photonics cannot be readily transferred and novel integrated architectures must be investigated. In this PhD you will be responsible for exploring a novel patent pending architecture for efficient and fast modulation of visible wavelengths. You will be conducting a theoretical and numerical analysis of new device stacks, fabricate those devices in collaboration with imec’s fabrication teams, and characterize the fabricated devices. While design and numerical analysis is part of the PhD, it should be stressed that the fabrication and experimental part will form the main focus of the work.

As an ideal candidate you:

• Have a Master in Photonics Engineering, Engineering Physics, Electronics, or Physics (or equivalent)
• Have a strong interest in experiment and fabrication
• Have strong English communication skills

Basic knowledge of the following is a plus but not a requirement:

• Python programming
• Device simulators for photonics (Lumerical FDTD/MODE, COMSOL)
• Semiconductor manufacturing processes for photonics
• Basic quantum mechanics

For more information, please contact

frederic.peyskens@imec.be