Search

Quantum computation features known examples of hardware acceleration for certain problems, but is challenging to realize because of its susceptibility to small errors from noise or imperfect control. The principles of fault tolerance may enable computational acceleration with imperfect hardware, but they place strict requirements on the character and correlation of errors1. For many qubit technologies2–21, some challenges to achieving fault tolerance can be traced to correlated errors arising from the need to control qubits by injecting microwave energy matching qubit resonances. Here we demonstrate an alternative approach to quantum computation that uses energy-degenerate encoded qubit states controlled by nearest-neighbour contact interactions that partially swap the spin states of electrons with those of their neighbours. Calibrated sequences of such partial swaps, implemented using only voltage pulses, allow universal quantum control while bypassing microwave-associated correlated error sources1,22–28. We use an array of six 28Si/SiGe quantum dots, built using a platform that is capable of extending in two dimensions following processes used in conventional microelectronics29. We quantify the operational fidelity of universal control of two encoded qubits using interleaved randomized benchmarking30, finding a fidelity of 96.3% ± 0.7% for encoded controlled NOT operations and 99.3% ± 0.5% for encoded SWAP. The quantum coherence offered by enriched silicon5–9,16,18,20,22,27,29,31–37, the all-electrical and low-crosstalk-control of partial swap operations1,22–28 and the configurable insensitivity of our encoding to certain error sources28,33,34,38 all combine to offer a strong pathway towards scalable fault tolerance and computational advantage.

Control over the morphology of calcium carbonate (CaCO 3 ) crystals has been achieved through the use of anionic, amphiphilic block copolypeptides during crystallization. Microspheres of CaCO 3 can be synthesized by the introduction of preformed organic, amphiphilic block copolypeptide templates, poly( l -aspartate sodium salt) 100 - block -[poly( l -phenylalanine) 25 - random -( l -leucine) 25 ] ( 1 ) and poly( l -glutamate sodium salt) 100 - block -[poly( l -phenylalanine) 25 - random -( l -leucine) 25 ] ( 2 ). When cationic amphiphiles are used in lieu of the anionic amphiphiles, only CaCO 3 rhombohedra are produced. The self-assembling amphiphile controls the precipitation of the microspheres by acting as a template to form giant CaCO 3 microspheres. These microspheres are composed of nanocrystals ranging in size from 10 to 60 nm using 1 and 20 to 100 nm using 2 .

A versatile "top-down" method for the fabrication of particles, Particle Replication In Nonwetting Templates (PRINT), is described which affords absolute control over particle size, shape, and composition. This technique is versatile and general enough to fabricate particles with a variety of chemical structures, yet delicate enough to be compatible with sophisticated biological agents. Using PRINT, we have fabricated monodisperse particles of poly(ethylene glycol diacrylate), triacrylate resin, poly(lactic acid), and poly(pyrrole). Monodisperse particle populations, ranging from sub-200 nm nanoparticles to complex micron-scale objects, have been fabricated and harvested. PRINT uses low-surface energy, chemically resistant fluoropolymers as molding materials, which eliminates the formation of a residual interconnecting film between molded objects. Until now, the presence of this film has largely prevented particle fabrication using soft lithography. Importantly, we have demonstrated that PRINT affords the simple, straightforward encapsulation of a variety of important bioactive agents, including proteins, DNA, and small-molecule therapeutics, which indicates that PRINT can be used to fabricate next-generation particulate drug-delivery agents.

We demonstrate that highly crystalline, monodisperse maghemite (γ-Fe2O3) nanoparticles, synthesized in organic solvents, can be effectively transferred into an aqueous medium using an ammonium salt and stabilized at neutral pH. The nanoparticles remain monodisperse, as characterized by TEM and XRD, as well as superparamagnetic, as determined by SQUID magnetometry. When the aqueous maghemite is combined with the block copolypeptide poly(EG2-lys)100-b-poly(asp)30, the nanoparticles assemble into uniform clusters comprised of approximately 20 nanoparticles, resulting in a water soluble block copolypeptide−nanoparticle composite structure.

Nanoparticle vesicles were spontaneously assembled from homopolymer polyamine polyelectrolytes and water-soluble, citrate-stabilized quantum dots. The further addition of silica nanoparticles to a solution of quantum dot vesicles generated stable micrometer-sized hollow spheres whose walls were formed of a thick, inner layer of close-packed quantum dots followed by an outer layer of silica. The method employed here to assemble both the nanoparticle vesicles and the hollow spheres is in direct contrast to previous syntheses that use either tailored block copolymers or oil-in-water emulsion templating. We propose that the formation of charge-stabilized hydrogen bonds between the positively charged amines of the homopolymer polyelectrolytes and the negatively charged citrate molecules stabilizing the quantum dots is responsible for the macroscopic phase separation in this completely aqueous system. The ease and processibility of the present approach gives promise for the production of a diverse array of materials ranging in applications from drug delivery to catalysis to micrometer-scale optical devices.

Transpiration of water at 5.6 μg/s through a bio-inspired hydrogel-microchannel synthetic tree is reported. Cavitation events in the synthetic tree induced by puncture, convective heating in air, and mechanical impact are imaged using a high speed camera at 16,326 pictures per second. Vapor bubbles generated from cavitation events propagate through the microchannels at speeds between 0.4 and 60 m/s depending on the inducement mode, demonstrating the need for cavitation protection features in synthetic trees. Partial cavitation protection is conferred to the synthetic tree by a parallel microchannel design.

This tutorial review presents an overview of strategies for the synthesis and fabrication of organic nanomaterials, specifically those with potential for use in medical applications. Examples include liposomes, micelles, polymer-drug conjugates and dendrimers. Methods of driving shape via"bottom-up" synthetic approaches and thermodynamics and kinetics are discussed. Furthermore, methods of driving shape via"top-down" physical and engineering techniques are also explored. Finally, a novel method (referred to as PRINT) used to produce nanoparticles that are shape-specific, can contain any cargo, and can be easily modified is examined along with its potential future role in nanomedicine.

The delivery of therapeutic, detection and imaging agents for the diagnosis and treatment of cancer patients has improved dramatically over the years with the development of nano-carriers such as liposomes, micelles, dendrimers, biomolecules, polymer particles, and colloidal precipitates. While many of these carriers have been used with great success in vitro and in vivo , each suffers from serious drawbacks with regard to stability, flexibility, or functionality. To date, there has been no general particle fabrication method available that afforded rigorous control over particle size, shape, composition, cargo and chemical structure. By utilizing the method we has designed referred to as P article R eplication I n N on-wetting T emplates, or PRINT , we can fabricate monodisperse particles with simultaneous control over structure ( i.e. shape, size, composition) and function ( i.e. cargo, surface structure). Unlike other particle fabrication techniques, PRINT is delicate and general enough to be compatible with a variety of important next-generation cancer therapeutic, detection and imaging agents, including various cargos (e.g. DNA, proteins, chemotherapy drugs, biosensor dyes, radio-markers, contrast agents), targeting ligands (e.g. antibodies, cell targeting peptides) and functional matrix materials (e.g. bioabsorbable polymers or stimuli responsive matrices). PRINT makes this possible by utilizing low-surface energy, chemically resistant fluoropolymers as molding materials and patterned substrates to produce functional, harvestable, monodisperse polymeric particles.

The crystallization of calcium carbonate into microspheres has been accomplished using the rationally-designed, doubly-hydrophilic block copolypeptide poly(Nepsilon-2[2-(2-methoxyethoxy)ethoxy]acetyl-L-lysine)(100)-b-poly(L-aspartate sodium salt)30 as a structure-directing agent.