Multiplexed Quantum Integrated Circuits
Lead Research Organisation:
University of Cambridge
Department Name: Physics
Abstract
The low-temperature multiplexer for quantum devices has allowed competing theories regarding quantum transport in interacting low-dimensional systems to be tested against experiment and because of the large numbers of devices that can be tested at once, a statistical approach to quantum nano-device physics discovery can be used. We induced superconductivity in two-dimensional electron gases and are searching for Majorana fermions. In this project, we want to proceed on several fronts, all using integrated circuits of split-gate transistors, to explore new physics, new technology and new electronics. This project will be supplemented (by other local projects and by the input from others using our facilities) so that most of the following topics will be pursued over the next three years: (* = core part of this project)
1. A gigahertz multiplexer*
2. Superconducting/semiconducting integrated circuits including topological insulator material addressed using the multiplexer*
3. Nanowire integrated circuits coupled to superconductors for investigating how robust Majorana modes are and exploring whether they could be reliably used for quantum technology*
4. Independent biasing through specific charge storage on each gate
5. Nanoscale multiplexer
6. A voltage camera circuit on the micron-scale
7. Multiplexers with induced 2DEGs to reduce fluctuations*
8. Single electron pumping in quantum dots in parallel to provide high current high accuracy pumps for a current standard*
9. Setting up a facility for external users*
1. A gigahertz multiplexer*
2. Superconducting/semiconducting integrated circuits including topological insulator material addressed using the multiplexer*
3. Nanowire integrated circuits coupled to superconductors for investigating how robust Majorana modes are and exploring whether they could be reliably used for quantum technology*
4. Independent biasing through specific charge storage on each gate
5. Nanoscale multiplexer
6. A voltage camera circuit on the micron-scale
7. Multiplexers with induced 2DEGs to reduce fluctuations*
8. Single electron pumping in quantum dots in parallel to provide high current high accuracy pumps for a current standard*
9. Setting up a facility for external users*
Planned Impact
This project will develop techniques that will allow hundreds of quantum nano-devices to be measured during the time that previously only one two could have been studied. Quantum nanodevices, when measured at low temperatures of a few kelvins above absolute zero, can show exotic quantum behaviour especially when two different materials are coupled together. The electrons in these systems can couple in new ways to behave, for example, like a new quasi-particle called a Majorana Fermion. It has been proposed that these Majorana Fermion quasi-particles can be used for quantum computing applications, but they are hard to observe, and the best conditions for observing them and manipulating them are only just being discovered. The multiplexer that will be used in this grant will allow hundreds of lightly different shaped devices to be made and tested to find and optimise how to robustly produce Majorana particles two different material systems. This will be very valuable to those working in quantum technology in this area. There will be a very large data set produced that those working in solid state theory can access to test their ideas on.
The development of a fast way to test multiple quantum devices will be of value to those who want to develop quantum technologies based on solid-state systems as we will develop data on how reliable and reproducible the physics we observe is.
In the long run, this research could help in the faster development of solid-state based quantum technology or will provide important information regarding a pathway to that goal. A quantum computer could, when developed, be used for fast materials discovery as such a computer would be ideally suited to model the quantum bonding found in new material systems. The discovery of new materials can then have an important impact on many areas, from energy generation and distribution to battery technology or biomedical application.
The development of a fast way to test multiple quantum devices will be of value to those who want to develop quantum technologies based on solid-state systems as we will develop data on how reliable and reproducible the physics we observe is.
In the long run, this research could help in the faster development of solid-state based quantum technology or will provide important information regarding a pathway to that goal. A quantum computer could, when developed, be used for fast materials discovery as such a computer would be ideally suited to model the quantum bonding found in new material systems. The discovery of new materials can then have an important impact on many areas, from energy generation and distribution to battery technology or biomedical application.
Publications
Behrends J
(2022)
Sachdev-Ye-Kitaev Circuits for Braiding and Charging Majorana Zero Modes.
in Physical review letters
Delfanazari K
(2023)
Large-Scale On-Chip Integration of Gate-Voltage Addressable Hybrid Superconductor-Semiconductor Quantum Wells Field Effect Nano-Switch Arrays
in Advanced Electronic Materials
Delfanazari K
(2024)
Quantized conductance in hybrid split-gate arrays of superconducting quantum point contacts with semiconducting two-dimensional electron systems
in Physical Review Applied
Delfanazari K
(2019)
Scalable Quantum Integrated Circuits on Superconducting Two-Dimensional Electron Gas Platform.
in Journal of visualized experiments : JoVE
Delfanazari K
(2020)
Integrated, Portable, Tunable, and Coherent Terahertz Sources and Sensitive Detectors Based on Layered Superconductors
in Proceedings of the IEEE
Jaliel G
(2019)
Experimental Realization of a Quantum Dot Energy Harvester.
in Physical review letters
Jaliel G
(2019)
Experimental Realization of a Quantum Dot Energy Harvester.
| Description | A chip has been fabricated and tested which allows the electrical properties of many different nanowires or 2d material samples to be tested from room temperature to cryogenic temperatures and up to high magnetic fields. This allows fast material development for many nano materials. Multiple devices have been tested that couple superconducting contacts to InAs quantum well semiconductor devices which contain spin orbit coupling. Induced superconductivity is observed and quantized 1D conductivity with enhanced conductance is also observed. Magneto-resistance shows magneto-oscillations which are under further investigation to understand their origin. Theoretical models for quantum states that sit in the mid gap of the induced superconducting gap in the semiconductor under the addition of an in-plane magnetic field. These states could potentially be used for quantum computation if they can be braided around each other. |
| Exploitation Route | This grant is a continuation grant which involved the purchase of a bottom loading dilution refrigerator. In this grant we have developed a cryogenic chip made from a GaAs GaAlAs heterostucture that can act as a multiplexer that allows up to 100 individual devices on one chip. The multiplexer was shown to be able to measure many graphene devices and many carbon nanotubes that can be placed on the mutiplexer chips. The chip was designed to work at both room temperature and low temperatures so devices can be checked before cooling to see if they work. The combined chip and cryostat will be set up as a facility for external users when the cryostat is moved to the new Ray Dolby building in later in the year. All system is ready for use. |
| Sectors | Digital/Communication/Information Technologies (including Software) Education Electronics Healthcare |
| URL | https://www.sp.phy.cam.ac.uk/research |
| Title | Built and demonstrated a GaAs GaAlAs heterostructure multiplexer chip that works from room temperature to sub 1K. |
| Description | The multiplexer chip allows individual graphene or nanowire devices to be addressed on the chip, checked at room temperature and then measured at cryogenic temperatures in a magnetic field. 16 device areas can be accessed with the chip. |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2020 |
| Provided To Others? | Yes |
| Impact | We have been able to measure multiple graphene devices and measure the localisation as a function of device geometry and device mobility. |
| Title | Research data supporting "Automated Computer Vision-Enabled Manufacturing of Nanowire Devices" |
| Description | Figure2c,e: Detected spatial distribution, length and orientation of isolated InAs nanowires in a 1 × 1 mm^2 region. Figure 4: Transfer characteristics of automatically fabricated nanowire devices with (a) 0.5 µm channel length, (b) 1.0 µm channel length, (c) 2.0 µm channel length, and (d) 2.5 µm channel length at source-drain voltage VDS = 10 mV. (e) Statistical data of nanowire device misalignment measured from the center of the nanowire to the center of the electrode pattern. Statistical data of (f) on/off ratio, (g) peak current, and (h) threshold voltage measured in automatically fabricated nanowire devices. Figure S8: Statistical data of (a) mobility and (b) hysteresis measured in automatically fabricated nanowire devices. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2022 |
| Provided To Others? | Yes |
| URL | https://www.repository.cam.ac.uk/handle/1810/341921 |
| Title | Research data supporting 'Giant Magnetoresistance in a CVD Graphene Constriction' |
| Description | The zipped file contains the resistance and conductance data from measurements of graphene channels as a function of magnetic field, temperature, and source-drain bias. Data are provided in separate .txt files for each figure. The README.txt file contains the column information and units for plotting. Specific data included are: Figure 1: (1) Resistance of the primary graphene channel as a function of back gate voltage at magnetic field B = 0 T and temperature T = 0.29 K. (2) Derivative of resistance as a function of back gate voltage at different magnetic fields and back gate voltages. Figure 2: The graphene conductance as a function of magnetic field at temperatures T = 0.29, 0.6, 1, 2, 5, 8, 11.3, 14, 17.8 and 25 K. Figures 3 and 4: Graphene resistance as a function of total source-drain bias applied to the circuit at different back gate voltages V_G = 0.2, 0.26, and 0.32 V, at temperature T = 0.29 K. The graphene resistance at charge neutrality as a function of total source-drain bias is also provided at different temperatures T = 0.29, 2, 5, 8, 11.2, 14.1, 17.8, and 25 K. These data are measured at B = 0 T. Figure 5: Transfer characteristics from a second graphene device. (1) The resistance is given as a function of back gate voltage at magnetic fields B = 0, 3, 6, 9, and 12 T, at temperature T = 1.5 K. (2) The resistance as a function of back gate voltage and magnetic field. (3) The resistance as a function of back gate voltage at different temperatures T = 1.5, 5, 11, and 30 K, and magnetic field B = 12 T. (4) The maximum resistance of the charge neutrality peak 'a' near gate voltage ~42 V, and peak 'b' at gate voltage 18 V, as a function of B at T = 1.5 K. (5) The resistance of peaks 'a' and 'b' as a function of temperature at B = 12 T. Data contained in the supporting information is also provided. This includes: (1) The conductance of the primary graphene channel as magnetic field is swept at high carrier density, for temperatures from 0.29 to 25 K. (2) Graphene resistance as a function of total source-drain bias applied to the circuit at different back gate voltages V_G = 0.2, 0.28, 0.3, 0.32, 0.34, 0.38, 0.4, and 0.5 V, at temperature T = ~1.4 K. (3) Raman spectra of the graphene as a function of location over a 10 by 10 micron square area with a 1 micron grid spacing. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2022 |
| Provided To Others? | Yes |
| Impact | The data set was used in our published work. |
| URL | https://www.repository.cam.ac.uk/handle/1810/332887 |
| Description | Dr Kaveh Delfanazari Associate Professor Electronics and Nanoscale Engineering, University of Glasgow |
| Organisation | University of Glasgow |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | Dr Delfanazari moved to Glasgow University as a lecturer in 2020, from being a PDRA on the grant, but continued to collaborate on the goals of the project. He has focused on the superconducting proximity effect in InAs nanodevices. |
| Collaborator Contribution | Dr Delfanazari has been working with the student and PDRA on the grant in Cambridge. He has been produced test devices that were measured in Cambridge. These devices consisting of short Josephson junctions made frmo NiNb contacts made to an InAs quantum well. Split gates were defined on the surface allowing 1D constrictions to be formed in the quantum well that contained an induced superconducting layer. |
| Impact | doi.org/10.1103/PhysRevApplied.21.014051 doi.org/10.1109/TQE.2023.3266946 doi.org/10.1002/aelm.202300453 doi.org/10.3390/nano11112999 |
| Start Year | 2020 |
| Description | National Physical Laboratory |
| Organisation | National Physical Laboratory |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | We are building an RF multiplexer for pumping multiple quantum dots in parallel so that we can get a current standard where each dot generates a current i=ef where f is the pumping frequency and e is the charge on an electron. |
| Collaborator Contribution | We have had advice on multiplexer designs that will work at 1 GHz and help with the analysis of our results. |
| Impact | None yet. |
| Start Year | 2019 |
| Description | Professor Chennupati Jagadish the Australian National University |
| Organisation | Australian National University (ANU) |
| Country | Australia |
| Sector | Academic/University |
| PI Contribution | We have added the InAs nanowires that are made by Professor Jagadish at ANU to our multiplexer devices and measured these at low temperatures. We are providing feedback on the device properties to ANU. |
| Collaborator Contribution | We have received InAs nanowires that we have been measuring our multiplexer devices. |
| Impact | Once the nanowires are placed on the multiplexer we have been able to measure the device properties of a number of devices, both at room temperature and at low temperatures. It is early in the project but we also hope to add superconducting contact to these wires and add an in place B field to look for Majorana Fermions. |
| Start Year | 2019 |
| Description | Invited talk in high school |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Study participants or study members |
| Results and Impact | Our research group activities are presented to high school students. |
| Year(s) Of Engagement Activity | 2020 |