CMOS and beyond CMOS
Discover why imec is the premier R&D center for advanced logic & memory devices. anced logic & memory devices.
Connected health solutions
Explore the technologies that will power tomorrow’s wearable, implantable, ingestible and non-contact devices.
Life sciences
See how imec brings the power of chip technology to the world of healthcare.
Sensor solutions for IoT
Dive into innovative solutions for sensor networks, high speed networks and sensor technologies.
Artificial intelligence
Explore the possibilities and technologies of AI.
More expertises
Discover all our expertises.
Research
Be the first to reap the benefits of imec’s research by joining one of our programs or starting an exclusive bilateral collaboration.
Development
Build on our expertise for the design, prototyping and low-volume manufacturing of your innovative nanotech components and products.
Solutions
Use one of imec’s mature technologies for groundbreaking applications across a multitude of industries such as healthcare, agriculture and Industry 4.0.
Venturing and startups
Kick-start your business. Launch or expand your tech company by drawing on the funds and knowhow of imec’s ecosystem of tailored venturing support.

Nonlinear transmons

PhD - Leuven | About a week ago

A multilevel quantum system where each of the energy levels can be addressed unambiguously via a single microwave pulse

A transmon qubit can be thought of as a non-linear capacitor-inductor system where the inducting element is replaced by a pair of Josephson junctions. These provide the sufficient nonlinearities to result in a system with discreet energy levels, where each pair of consecutive levels are split out by a different energy. This makes possible to address the two lowest levels independently from the others and use the transmon as a two-level quantum mechanical system, i.e., a qubit.

Transmon qubits are typically capacitively coupled to resonators (transmission lines) and the qubit-resonator coupling is well described by the Jaynes-Cummings (or Tavis-Cummings) Hamiltonian. But this model has some limitations. One of them is that higher levels of the transmon qubit can only be excited sequentially after exciting the lowest ones. Of course this is usually regarded as an advantage, since for quantum computation purposes it is convenient to limit the Hilbert space to two states only and disregard higher states and their coupling to the resonator. But an extended coupling where we can selectively excite any transmon level can offer new possibilities for quantum information transmission and processing.

This extended behavior can be accomplished by replacing the conventional capacitor, which has an energy quadratic in the potential with a “nonlinear capacitor”. This is an element composed of two parallel plates—very much like a capacitor—with carbon nanotubes between the plates. This results into an energy containing an additional quartic term in the potential that depends on the details of the nanostructure [1,2]. The fabrication of such device has been shown to be feasible [3], but a theoretical description of such a system as well as an analysis of its possible applications is still missing. Furthermore the exploration for other materials or structures that can lead to such non-linear behavior will also be part of this PhD. 

[1] S. Ilani, L. Donev, M. Kindermann, et al. Nature Phys 2, 687–691 (2006).

[2] D. Akinwande, Y. Nishi and H. -. P. Wong, IEEE Transactions on Nanotechnology, 8, 31-36, (2009).

[3] M. Mergenthaler, A Nersisyan, A Patterson, et al. arXiv preprint arXiv:1904.10132.


Required background: Physics, Electrical engineering, Engineering physics

Type of work: 80% Modeling/simulation 20% literature

Supervisor: Christian Maes

Co-supervisor: Bart Soree

Daily advisor: Bart Soree

The reference code for this position is 2021-057. Mention this reference code on your application form.

This website uses cookies for analytics purposes only without any commercial intent. Find out more here. Our privacy statement can be found here. Some content (videos, iframes, forms,...) on this website will only appear when you have accepted the cookies.