Quantum Logic Processor: A Mach Zehnder Interferometer based Approach

Quantum Logic Processors can be implemented with Mach Zehnder Interferometer(MZI) configurations for the Quantum logic operations and gates. In this paper, its implementation for both optical and electronic system has been presented. The correspondence between Jones matrices for photon polarizations and Pauli spin matrices for electrons gives a representation of all the unitary matrices for the quantum gate operations. A novel quantum computation system based on a Electronic Mach Zehnder Interferometer(MZI) has also been proposed. It uses the electron spin as the primary qubit. Rashba effect is used to create Unitary transforms on spin qubits. A mesoscopic Stern Gerlach apparatus can be used for both spin injection and detection. An intertwined nanowire design is used for the MZI. The system can implement all single and double qubit gates. It can easily be coupled to form an array. Thus the Quantum Logic Processor (QLP) can be built using the system as its prototype.Comment: 19 pages, 6 figures, 8 Table

All Spin Logic device with inbuilt Non-Reciprocity

The need for low power alternatives to digital electronic circuits has led to increasing interest in logic devices where information is stored in nanomagnets. This includes both nanomagnetic logic (NML) where information is communicated through magnetic fields of nanomagnets and all-spin logic (ASL) where information is communicated through spin currents. A key feature needed for logic implementation is non-reciprocity, whereby the output is switched according to the input but not the other way around, thus providing directed information transfer. The objective of this paper is to draw attention to possible ASL-based schemes that utilize the physics of spin-torque to build in non-reciprocity similar to transistors that could allow logic implementation without the need for special clocking schemes. We use an experimentally benchmarked coupled spin-transport/ magnetization-dynamics model to show that a suitably engineered single ASL unit indeed switches in a non-reciprocal manner. We then present heuristic arguments explaining the origin of this directed information transfer. Finally we present simulations showing that individual ASL devices with inbuilt directionality can be cascaded to construct circuits.Comment: 7 pages, 8 figures, To appear in IEEE Trans. Mag

Information processing with spin-coupled multi-magnet networks

The speed and efficiency of information processing in conventional charge based field effect transistors have progressed dramatically in the last 50 years due to scaling of transistor dimensions. However, the fundamental scaling limits of this technology are threatening to halt this progress; leading to an enormous interest in alternative computation schemes and devices. All-spin logic (ASL) is one such alternative approach to information processing where information is stored in the magnetization of nanomagnets coupled by spin coherent channels. We developed an experimentally benchmarked spin-coupled multi-magnet simulator to investigate two major aspects of ASL operation. Firstly, we evaluated the energy (E) delay (τ) performance metric of ASL switches and found that similar to transistors, Eτ = Q2R where R is the resistance of the device and Q, total charge supplied by the power supply in the switching process is proportional to the number of Bohr Magnetons comprising the magnet. Secondly, we found that the inbuilt non-reciprocity in ASL allows cascading them to form spin-coupled multi-magnets networks (SMN) where universal logic gates, ring oscillator and other interesting circuits can be implemented. These circuits seem difficult to implement experimentally at this time, since the large magnets used today require very high threshold spin signal to switch. Hence, for ease of experimental implementation, we proposed a different class of devices which could operate at sub-threshold bias; but still rely on the spin torque based interaction between nanomagnets. We have also developed a generic framework that can be used to understand the results of such sub-threshold experiments on spin-coupled multi-magnets networks.