Periodic Reporting for period 3 - aCryComm (attojoule Cryogenic Communication)
Okres sprawozdawczy: 2023-10-01 do 2024-09-30
All envisaged practical implementations of cryogenic processors, including both quantum computers (QCs) and classical processors based on single flux quantum (SFQ) signals, require massive data transfer from and to classical high performance computers (HPCs). The EU-funded aCryComm project aims to develop building blocks for cryogenic photonics interconnects and eventually enable this challenging data transfer. The long-term goal is the development of an open-access platform to integrate classical optical interfaces based on low-loss silicon photonics, plasmonics, and nano light sources together with superconducting photonic and electronic devices, including SFQ-based co-processors for HPCs and for QCs. These developments will lead to more efficient, more powerful and greener supercomputers to help tackling relevant problems e.g. in modelling climate change or developing new drugs.
In WP1, VTT has significantly improved the reliability and minimized parameter scatter of their Josephson junction (JJ) process, which benefits multitude of applications also beyond aCryComm. At the early phases of the project, process changes toward minimized parameter scatter yielded problems with the fabrication of SFQ circuits and only very elementary SFQ-type behaviour was observed. However, VTT has also developed the fabrication of Josephson Arbitrary Waveform Synthesizer (JAWS) circuits with the same same JJ process and demonstrated Shapiro steps. These samples provide a more realistic way toward demonstrators in the near future than SFQ. Meanwhile, VTT, ETH, and Polariton have been studying possible interfaces that will allow to drive plasmonic modulators with SFQ (EO conversion) despite the large mismatch in energy per bit and operation voltage.
In WP2-3, ETH and Polariton have performed pioneering plasmonic experiments at cryogenic temperatures. Room temperature measurement data shows that ETH has developed the two fastest photodetectors in the world using graphene as the optically sensitive element. Limited by measurement, the fastest detector shows flat frequency response up to 500 GHz at room temperature and up to 100 GHz at 4 K. ETH and Polariton performed the MZM validation of Polariton's modulators with an electro-optic bandwidth above 100 GHz, low on-off and driving voltages, data transmission experiments proved data rates up to 128 Gbit/s, all at 4 K.
In parallel, TAU has been developing their alternative approach based on high efficiency microcavity light sources following two paths: vertical cavity surface emitting lasers and quantum dot nano light sources. A remarkable breakthrough is the development of quantum dots for operation in the telecom wavelength range around 1550 nm. Also TAU have been setting up a cryostat for characterization of the fabricated light sources. The development by TAU and KTH of light sources modulated by surface acoustic waves shows promising preliminary results, but further research beyond aCryComm is required. On the opto-electric conversion front, Single Quantum has developed ultra-short SNSPD devices, aiming at higher speed, and tackling the well-known latching problem.
PTB has demonstrated a optical cryogenic oscilloscope by measuring the time-domain response of a commercial photodiode. Measurements of aCryComm's novel OECs are planned. VTT has actively developed improved cryogenic optical and 3D packaging schemes for advanced demonstrators. The most ambitious demonstrator experiments will be performed after the project has ended.
In WP2-3, ETH and Polariton have performed pioneering plasmonic experiments at cryogenic temperatures. Room temperature measurement data shows that ETH has developed the two fastest photodetectors in the world using graphene as the optically sensitive element. Limited by measurement, the fastest detector shows flat frequency response up to 500 GHz at room temperature and up to 100 GHz at 4 K. ETH and Polariton performed the MZM validation of Polariton's modulators with an electro-optic bandwidth above 100 GHz, low on-off and driving voltages, data transmission experiments proved data rates up to 128 Gbit/s, all at 4 K.
In parallel, TAU has been developing their alternative approach based on high efficiency microcavity light sources following two paths: vertical cavity surface emitting lasers and quantum dot nano light sources. A remarkable breakthrough is the development of quantum dots for operation in the telecom wavelength range around 1550 nm. Also TAU have been setting up a cryostat for characterization of the fabricated light sources. The development by TAU and KTH of light sources modulated by surface acoustic waves shows promising preliminary results, but further research beyond aCryComm is required. On the opto-electric conversion front, Single Quantum has developed ultra-short SNSPD devices, aiming at higher speed, and tackling the well-known latching problem.
PTB has demonstrated a optical cryogenic oscilloscope by measuring the time-domain response of a commercial photodiode. Measurements of aCryComm's novel OECs are planned. VTT has actively developed improved cryogenic optical and 3D packaging schemes for advanced demonstrators. The most ambitious demonstrator experiments will be performed after the project has ended.
Ultrafast plasmonic photodetectors and modulators operating at cryogenic temperatures are a major step beyond the state of the art. In addition, the consortium has demonstrated an ultrafast sampling oscilloscope operating at cryogenic temperatures. All of these breakthroughs demonstrate the opportunities of combining optical and electronic technologies at cryogenic temperatures. The aCryComm project studies technologies at an early level of readiness, but eventually we expect that optical communication will enable a step change in the scalability and energy-efficiency of cryogenic technologies. For example, the power consumption per qubit is intolerable in present superconducting quantum computers, largely due to heat conduction from electrical cabling. The ultimate impact will be on high performance computing, which we expect to lead to significant benefit to major problems of our society, including modelling of climate changes and development of drugs. We have also identified the possible application of aCryComm developments to boost quantum key distribution systems, which will support the development of the European quantum communication infrastructure.