Due to their excellent electrical properties, metallic carbon nanotubes are promising materials for interconnect wires in future integrated circuits. Simulations have shown that the use of metallic carbon nanotube interconnects could yield more energy efficient and faster integrated circuits. The next step is to build an experimental prototype integrated circuit using carbon nanotube interconnects operating at high speed. Here, we report the fabrication of the first stand-alone integrated circuit combining silicon transistors and individual carbon nanotube interconnect wires on the same chip operating above 1 GHz. In addition to setting a milestone by operating above 1 GHz, this prototype is also a tool to investigate carbon nanotubes on a silicon-based platform at high frequencies, paving the way for future multi-GHz nanoelectronics.

We propose a method to efficiently generate cluster states in charge qubits, both semiconducting and superconducting, as well as flux qubits. We show that highly-entangled cluster states can be realized by a 'one-touch' entanglement operation by tuning gate bias voltages for charge qubits. We also investigate the robustness of these cluster states for non-uniform qubits, which are unavoidable in solid-state systems. We find that quantum computation based on cluster states is a promising approach for solid-state qubits.PACS numbers: 03.67. Lx, 03.67.Mn, 73.21.La One-way quantum computing [1], which is based on a series of one-qubit measurements starting from cluster states of a qubit array, is an intriguing alternative to the widely studied approach using unitary quantum gates. Here, the power of quantum mechanics, such as quantum parallelism and entanglement, is already stored in the initial cluster state. Cluster states are fixed highlyentangled states that involve all qubits and act as a universal resource for quantum computing.Because of their unique importance, cluster states have been studied in a variety of physical systems. They have been extensively explored in optical quantum computers both theoretically [2] and experimentally [3]. By incorporating cluster states, optical quantum computing can achieve substantially simpler operations [2] compared to the original linear optics quantum computing proposal [4]. Cluster states have also been studied in solid state qubits. In particular, processes of generating cluster states for single and encoded spin qubits have been proposed [5,6] using the Heisenberg exchange interaction.The existing methods of generating cluster states all require multiple steps because of the types of interaction involved (in the case of photonic qubits, a large number of optical elements is also required). Here we describe theoretically an efficient method to create scalable cluster states in charge qubits [7,8,9,10,11,12,13] and flux qubits [14,15,16], using existing Ising-like interactions. Our key result is that cluster states in charge qubits can be created by applying a single gate bias pulse, right after preparing an initial product state |Ψ 0 ≡ |Ψ(t = 0) = Π i |+ i , whereWe also calculate the time-dependent fidelity of the cluster states in charge qubits using a quantum dot (QD) system with decoherence produced by the measurement back-action, and explore the effects of non-uniformity among qubits, which is a realistic characteristics for all solid-state qubits.Cluster states in charge qubits.-The Hamiltonian for an array of charge qubits with nearest-neighbor interactions is described bywith Pauli matrices σ ix and σ iz for the i-th qubit. Ω i is either the inter-QD tunnel coupling for coupled QD systems [7,8,9], or half the Josephson energy for superconducting charge qubits [11,12,13], respectively. For either semiconducting or superconducting charge qubits, ǫ i is the charging energy, and corresponds to the energy difference between |0 and |1 for each qubit. The coupling ...

Most parts of present computer systems are made of volatile devices, and the power to supply them to avoid information loss causes huge energy losses. We can eliminate this meaningless energy loss by utilizing the non-volatile function of advanced spin-transfer torque magnetoresistive random-access memory (STT-MRAM) technology and create a new type of computer, i.e., normally off computers. Critical tasks to achieve normally off computers are implementations of STT-MRAM technologies in the main memory and low-level cache memories. STT-MRAM technology for applications to the main memory has been successfully developed by using perpendicular STT-MRAMs, and faster STT-MRAM technologies for applications to the cache memory are now being developed. The present status of STT-MRAMs and challenges that remain for normally off computers are discussed.

Carbon-based nanomaterials such as metallic singlewalled carbon nanotubes, multiwalled carbon nanotubes (MWCNTs), and graphene have been considered as some of the most promising candidates for future interconnect technology because of their high current-carrying capacity and conductivity in the nanoscale, and immunity to electromigration, which has been a great challenge for scaling down the traditional copper interconnects. Therefore, studies on the performance and optimization of carbon-based interconnects working in a realistic operational environment are needed in order to advance the technology beyond the exploratory discovery phase. In this paper, we present the first demonstration of graphene interconnects monolithically integrated with industry-standard complementary metal-oxide-semiconductor technology, as well as the first experimental results that compare the performance of high-speed on-chip graphene and MWCNT interconnects. The graphene interconnects operate up to 1.3-GHz frequency, which is a speed that is commensurate with the fastest high-speed processor chips today. A low-swing signaling technique has been applied to improve the speed of carbon interconnects up to 30%.