Full-adder based on coherent quantum dynamics for energy efficient computing

Summary of the technology

Design of a quantum based single-bit full-adder with greater energy efficiency than currently existing transistor-based technologies. The encoding of information in only a few electrons trapped inside a semiconductor system of three quantum dots allows the execution of a full-adder through coherent quantum dynamics, which are inherently energy conservative.

Instituto de Telecomunicações


Current semiconductor technology is reaching its limits, with further miniaturization incurring heavy thermal loads due to the dissipative nature of transistor-based devices, which will subsequently lead the performance to plateau. At the same time, over the past decades, the research and development of quantum computation has grown exponentially.

The proposed technology is a spin-off from this research, where the main purpose is, instead, to exploit a binary encoding of logic in low-energy quantum states to do classical computation with reduced energy cost. Related technologies (e.g. Quantum Dot Cellular Automata) have been proposed for energy efficient computation, however their experimental development has been hindered by the complexity of the devices, which require dozens of quantum dots for even the simplest operations. The presentmodel uses a triple quantum dotsystemto execute the addition of two bits through a series ofFredkin gates, which swap the state of two bits conditional on a third bit.The sum of two bits is a fundamental operation in any computer’s Arithmetic and Logic Unit (ALU). Thedynamics of theFredkin gateareimplemented through the quantum coherent dynamics of electrons tunneling between the quantum dots, which are inherently conservative.


  • High-Performance Computing (HPC) Systems
  • Very Large Scale Integration (VLSI) Circuits
  • Large-scale data centers
  • Reversible computing


  • SIGNIFICANTLY IMPROVED ENERGY EFFICIENCY of future computing technologies, specially in the realm of HPC systems. Simulations of the proposed full-adder highlight a potential energetic cost in themilli electron-volt ranges several orders of magnitude below current transistor-based full-adders.
  • COMPATIBILITY WITH INDUSTRIAL STANDARDS IN SEMICONDUCTOR FABRICATION: the usage of semiconductor quantum dots is a great advantage given their compatibility with the currently advanced industrial standards.


TRL 2 -Theoretical model based on a realistic, experimentally verified triple quantum dot system. Simulations show the full-adder can be operated with a wide range of realistic parameters, allowing flexibility in the implementation. Given that other triple quantum dot systems have been demonstrated in a lab environment for other purposes, a first proof-of-concept experiment for this technology to achieve TRL 3 is expected to be straightforward.


  • Licensing or assignment agreement
  • Joint further theoretical and experimental developments


Instituto deTelecomunicações seeks partners within industry or R&D, working on chip manufacturing, semiconductor technologies or quantum computing.


Patent application filed in Portugal (PT116602)

International Patent Application (PCT/PT2021/050022) with excellent ISR and WO (priority date: 24-07-2020)


J.P. Moutinho,M.Pezzutto,F.Silva,S.Franceschi, S.Bose,AT. Costa andY.Omar,“Quantumcoherence for energetic advantage in a charge basedfull-adder”,inpreparation.







Intellectual property status

Attached documents

Related Keywords

  • Electronics, IT and Telecomms
  • Electronics, Microelectronics
  • Advanced Systems Architecture
  • Computer Hardware
  • Computer Technology/Graphics, Meta Computing
  • Information Technology/Informatics
  • Electronic circuits, components and equipment
  • Quantum Informatics
  • Semiconductors Technology
  • Computer related
  • Computers

About Instituto de Telecomunicações

Instituto de Telecomunicações (IT) is a private, not-for-profit organization, of public interest, a partnership of nine institutions with research and development in the field of Telecommunications

IT mission is to create and disseminate scientific knowledge in the field of telecommunications.

IT is actively involved in fundamental and applied research both at national and international levels. Simultaneously it is committed to foster higher education and training, by hosting and tutoring graduate and postgraduate students. it also plays its role towards public society with public awareness initiatives, knowledge transfer to industry, and by providing consulting services on a non-competing basis.

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