University of Sheffield - Equipment Account

应用量子规则而不是经典物理，对我们如何操纵信息有很大的不同。一个经典的“位”数据可以有两个值之一，“0”或“1”。它的量子对应物，量子位，可以处于这两个值的叠加状态，也就是说同时具有这两个值。这一点，再加上量子纠缠（爱因斯坦的“幽灵般的”远距离作用），可以使量子计算机的性能大大超过当前的计算机。然而，制造这样的机器是非常困难的；在控制大型量子系统的同时，将它们与环境充分隔离，以便能够进行有用的计算，这是一项挑战。目前，使用许多不同种类的硬件（捕获离子，纳米开尔文温度下的原子，超导电路，硅波导中的单光子），可以在几个量子位的阵列上执行一些简单的量子算法。然而，对于所有这些系统来说，将这些演示器扩展到有用的设备上存在着非常重大的挑战。我们建议使用不同的技术开发量子电路，III-V半导体材料（GaAs, AlGaAs， InGaAs等）。我们的电路将使用光子和电子自旋作为量子比特，利用III-V材料的光学特性来执行量子操作。III-V型半导体的一大优势是成熟的光子学技术和先进的制造能力已经存在，这将使我们能够将电路的所有元件放在单个微芯片上。有了这种级别的集成，我们的方法本质上是可伸缩的。我们的五年愿景是构建包含实现量子信息处理所需的所有基本构建模块的电路：生成光子量子比特的单光子源，量子比特之间的通信通道，量子逻辑门，由自旋量子比特组成的存储器，以及片上单光子探测器。这种类型的电路可以构成未来量子计算机的基石，但它们也可以在大规模量子计算领域之外执行有用的量子功能。有了这种复杂程度，就有可能构建量子中继器，实现大规模的安全量子通信网络。在量子计量学中也有应用，量子力学的特性可以用来获得超越经典物理学所施加的基本限制的精度。潜在的受益领域是磁传感器和显微镜。为了实现集成量子技术的这一愿景，我们必须推动半导体物理和器件制造领域的最新技术。在物理方面，我们期望的重点包括展示对设备中核自旋的完全控制，在芯片上获得远程量子比特的纠缠，创建光子封锁结构，其中单个光子的存在可以阻止更多的光子进入，以及在单量子尺度上开发光-物质相互作用的控制。技术方面的目标同样具有挑战性，包括调整量子点特性以实现严格控制的发射特性，在光学腔中集成的指定位置上的点的生长，以及高度可复制的光刻以实现高效的电路性能。所有这些主题都将是我们目标的核心，并将在提案中讨论；此外，它们对广泛的相关纳米光子技术具有潜在的意义。

Applying the rules of quantum rather than classical physics makes big differences to how we can manipulate information. A classical 'bit' of data can have one of two values, '0' or '1'. Its quantum counterpart, the qubit, can be in a state which is a superposition of the two values, in the sense of having both values at the same time. This, along with entanglement (Einstein's 'spooky' action at a distance) could enable quantum computers to out-perform current computers by huge margins. However making such a machine is very difficult; it is challenging to control large quantum systems while simultaneously isolating them from their environment sufficiently well to be able to carry out a useful calculation. Currently, using a number of different sorts of hardware (trapped ions, atoms at nano-Kelvin temperatures, superconducting circuits, single photons in silicon waveguides), it is possible to perform some simple quantum algorithms on arrays of a few qubits. However, for all these systems, there are very significant challenges to scaling such demonstrators up into useful devices. We propose to develop quantum circuits using a different technology, III-V semiconductor materials (GaAs, AlGaAs, InGaAs etc). Our circuits will employ photons and electron spins as qubits, making use of the optical properties of the III-V materials to carry out the quantum operations. A big advantage of the III-V semiconductors is that a mature photonics technology with advanced fabrication capabilities already exists, which will enable us to put all the elements of a circuit on a single microchip. With this level of integration, our approach is intrinsically scalable. Our five year vision is to construct circuits containing all the basic building blocks required to achieve quantum information processing: single photon sources to generate photon qubits, communication channels between qubits, quantum logic gates, memories consisting of spin qubits, and on-chip single photon detectors. Circuits of this type could form the building blocks of future quantum computers, but they can also perform useful quantum functions outside the realm of large scale quantum computation. With this level of complexity, it is possible to build quantum repeaters that enable wide-scale secure quantum communication networking. There are also applications in quantum metrology, where the properties of quantum mechanics can be used to obtain precision beyond the fundamental limits imposed by classical physics. Potential areas that may benefit here are magnetic sensors and microscopy. To pursue this vision of an integrated quantum technology, we will have to push forward the state of the art in semiconductor physics and device fabrication. On the physics side, our expected highlights include demonstrating full control of the nuclear spins in a device, obtaining entanglement of remote qubits on a chip, creating photon blockade structures, where the presence of a single photon prevents any more from entering, and developing control of light-matter interactions on the scale of single quanta. The targets on the technology side are equally challenging and will include tuning of quantum dot properties to achieve tightly controlled emission properties, the growth of dots in defined positions for incorporation in optical cavities, and highly reproducible lithography to achieve efficient circuit performance. All these topics will be central to our goals and will be addressed within the proposal; in addition they have potential to be of significance for a wide range of related nanoscale photonic technologies.