Electron-photon small-talk could have big impact on quantum computing

In a step that brings silicon-based quantum computers closer to reality, researchers have built a device in which a single electron can pass its quantum information to a particle of light.

Read More...

Comments Off on Electron-photon small-talk could have big impact on quantum computing

The sound of quantum vacuum

Quantum mechanics dictates sensitivity limits in the measurements of displacement, velocity and acceleration. A recent experiment probes these limits, analyzing how quantum fluctuations set a sensor membrane into motion in the process of a measurement. The membrane is an accurate model for future ultraprecise quantum sensors, whose complex nature may even hold the key to overcome fundamental quantum limits.

Read More...

Comments Off on The sound of quantum vacuum

One step closer to reality: Devices that convert heat into electricity

The same researchers who pioneered the use of a quantum mechanical effect to convert heat into electricity have figured out how to make their technique work in a form more suitable to industry.

Read More...

Comments Off on One step closer to reality: Devices that convert heat into electricity

Atomic clock mimics long-sought synthetic magnetic state

Physicists have caused atoms in a gas to behave as if they possess unusual magnetic properties long sought in harder-to-study solid materials.

Read More...

Comments Off on Atomic clock mimics long-sought synthetic magnetic state

Multi-user quantum key distribution with entangled photons from an AlGaAs chip

In view of real-world applications of quantum information technologies, the combination of miniature quantum resources with existing fibre networks is a crucial issue. Among such resources, on-chip entangled photon sources play a central role for applications spanning quantum communications, computing and metrology. Here, we use a semiconductor source of entangled photons operating at room temperature in conjunction with standard telecom components to demonstrate multi-user quantum key distribution, a core protocol for securing communications in quantum networks. The source consists of an AlGaAs chip-emitting polarisation entangled photon pairs over a large bandwidth in the main telecom band around 1550 nm without the use of any off-chip compensation or interferometric scheme; the photon pairs are directly launched into a dense wavelength division multiplexer (DWDM) and secret keys are distributed between several pairs of users communicating through different channels. We achiev… …

Read More...

Comments Off on Multi-user quantum key distribution with entangled photons from an AlGaAs chip

A transmon quantum annealer: decomposing many-body Ising constraints into pair interactions

Adiabatic quantum computing is an analogue quantum computing scheme with various applications in solving optimisation problems. In the parity picture of quantum optimization, the problem is encoded in local fields that act on qubits that are connected via local four-body terms We present an implementation of a parity annealer with Transmon qubits with a specifically tailored Ising interaction from Josephson ring modulators. …

Read More...

Comments Off on A transmon quantum annealer: decomposing many-body Ising constraints into pair interactions

An efficient magic state approach to small angle rotations

Standard error-correction techniques only provide a quantum memory and need extra gadgets to perform computation. Central to quantum algorithms are small angle rotations, which can be fault-tolerantly implemented given a supply of an unconventional species of magic state. We present a low-cost distillation routine for preparing these small angle magic states. Our protocol builds on the work of Duclos-Cianci and Poulin (2015 Phys. Rev. A 91 [http://10.1103/PhysRevA.91.042315] 042315 ) by compressing their circuit. Additionally, we present a method of diluting magic states that reduces costs associated with very small angle rotations. We quantify performance by the expected number of noisy magic states consumed per rotation, and compare with other protocols. For modest-sized angles, our protocols offer a factor 24 improvement over the best-known gate synthesis protocols and a factor 2 over the Duclos-Cianci and Poulin protocol. For very small angle rotati… …

Read More...

Comments Off on An efficient magic state approach to small angle rotations

Simple method of generating and distributing frequency-entangled qudits

High-dimensional, frequency-entangled photonic quantum bits (qudits for d -dimension) are promising resources for quantum information processing in an optical fiber network and can also be used to improve channel capacity and security for quantum communication. However, up to now, it is still challenging to prepare high-dimensional frequency-entangled qudits in experiments, due to technical limitations. Here we propose and experimentally implement a novel method for a simple generation of frequency-entangled qudts with ##IMG## [http://ej.iop.org/images/2058-9565/1/1/015004/qstaa4944ieqn1.gif] {$d\gt 10$} without the use of any spectral filters or cavities. The generated state is distributed over 15 km in total length. This scheme combines the technique of spectral engineering of biphotons generated by spontaneous parametric down-conversion and the technique of spectrally resolved Hong-Ou-Mandel interference. Our frequency-entangled qudits will enable … …

Read More...

Comments Off on Simple method of generating and distributing frequency-entangled qudits