Quantum dot 似乎有两种原理：一种像半导体器件，一种是试剂溶液

[TheMatrix]

这是第一种：利用Coulomb blockade原理。

[TheMatrix]

这是试剂溶液方式：

[TheMatrix]

Nature uses 20 canonical amino acids as building blocks to make proteins, combining their sequences to create complex molecules that perform biological functions.

But what happens with the sequences not selected by nature? And what possibilities lie in constructing entirely new sequences to make novel (de novo) proteins bearing little resemblance to anything in nature?

That's the terrain where Michael Hecht, professor of chemistry, works with his research group. Recently, their curiosity for designing their own sequences paid off.

They discovered the first known de novo (newly created) protein that catalyzes (drives) the synthesis of quantum dots. Quantum dots are fluorescent nanocrystals used in electronic applications from LED screens to solar panels.

And because they're small—composed of only about 100 atoms and maybe 2 nanometers across—they're able to penetrate some biological barriers, making their utility in medicines and biological imaging especially promising.

Why use de novo proteins?

"I think using de novo proteins opens up a way for designability," said Leah Spangler, lead author on the research and a former postdoc in the Scholes Lab. "A key word for me is 'engineering.' I want to be able to engineer proteins to do something specific, and this is a type of protein you can do that with.

[verdelite]

不太看得懂。像电子一样大的晶体？要知道电子是非常非常小的，现代方法都还没找到下限。

还有，最后一个图，bar是两纳米的，那么小的dots, 能分辨出来吗？可见光波长差不多也有500纳米了吧。超分辨率显微镜，我上次看到时候（他们得奖的时候）也差不多也就1/10瑞利极限，这都小于1/1000了。是合成的显微照片吗？

[TheMatrix]

应该用protein quantum dots.

[TheMatrix]

[Caravel]

这种化学方法长出来的，要后面才能搭电极上去，应用比较有限。半导体技术制备的可以事先有plan

[craigthone]

我感觉就一种解释，就是Coulomb repulsion.第二种可以用第一种的解释，光与电子的作用就可以解释吧。

[TheMatrix]

我感觉就一种解释，就是Coulomb repulsion.第二种可以用第一种的解释，光与电子的作用就可以解释吧。

你是说试剂溶液那个，也是Coulomb repulsion 的原理？

[craigthone]

你是说试剂溶液那个，也是Coulomb repulsion 的原理？

我不是专家，但我的感觉是那个化学现象来自光和电子相互作用，吸收和辐射。不应该有更基本的解释。

[TheMatrix]

A research group led by Prof. Wu Kaifeng from the Dalian Institute of Chemical Physics (DICP), Chinese Academy of Sciences recently reported the successful initialization, coherent quantum-state control, and readout of spins at room temperature using solution-grown quantum dots, which represents an important advance in quantum information science.

The study was published in Nature Nanotechnology on Dec 19th.

Quantum information science is concerned with the manipulation of the quantum version of information bits (called qubits). When people talk about materials for quantum information processing, they usually think of those manufactured using the most cutting-edge technologies and operating at very cold temperatures (below a few Kelvin), not the "warm and messy" materials synthesized in solution by chemists.

Recent years have witnessed the discovery of isolated defects in solid-state materials (such as NV centers) that have made possible room-temperature spin-qubit manipulation, but scaled-up production of these "point defects" will eventually become a challenge.

Colloidal quantum dots (QDs), which are tiny semiconductor nanoparticles made in solution, could be a game changer. They can be synthesized in large quantities in solution at low cost, yet with high finesse in size and shape control.

Further, they are usually strongly quantum-confined, thus their carriers well isolated from the phonon bath, which could enable long-lived spin coherence at room temperature. But room-temperature coherent manipulation of spins in colloidal QDs has never been reported, in that a QD system whose spins can be simultaneously initialized, rotated, and readout at room-temperature remains to be invented.

Here the authors show that solution-grown CsPbBr3 perovskite QDs can actually accomplish this intimidating goal. Polarized hole spins are obtained by sub-picosecond electron scavenging, to surface-anchored molecular acceptors, following a circularly-polarized femtosecond pulse excitation.

A transverse magnetic field induces coherent Larmor precession of the hole spins. A second off-resonance femtosecond pulse coherently rotates the spins through the optical Stark effect, which is enabled by the exceptionally strong light-matter interaction of the perovskite QDs. These results represent full quantum-state control of single-hole spins at room temperature, holding great promise for a scalable and sustainable future of spin-based quantum information processing

"Our success here is enabled by a very rare combination of knowledge in materials, chemistry and physics," said Prof. Wu. "We fabricated strongly- and uniformly-confined CsPbBr3 QDs as the unique system for the study, and identified appropriate surface-ligand molecules to rapidly extract the electrons via charge-transfer chemistry for hole-spin initialization at room temperature. Meanwhile, we were able to utilize strong light-matter interaction of these QDs to perform coherent spin manipulation."

[Caravel]

quantum dot在物理里面不是指的同一个东西，size比较小的structure能体现quantum effect的都可以marketing成quantum dot，有做单电子transistor的，也有做发光器件的，还有量子计算的。

[verdelite]

quantum dot在物理里面不是指的同一个东西，size比较小的structure能体现quantum effect的都可以marketing成quantum dot，有做单电子transistor的，也有做发光器件的，还有量子计算的。

坚决反对把电子分为一个一个电子这事称为“quantum effect”。quantum theory指的是波尔的电子运动角动量量子化、能级、跃迁、（爱因斯坦的）光子概念，还有新量子论（海森堡、薛定谔、狄拉克的波函数、其特征值对应的能量量子化、跃迁、光子概念。

电子是一个一个的，还有质子、中子是一个一个的，原子、分子是一个一个的，这些都不是quantum effect 。那些把油滴很小所以带一个电子也能测出（例如密立根油滴实验）电荷变化的事称为quantum effect的，是在碰瓷quantum这个“高档”词汇。

[Caravel]

坚决反对把电子分为一个一个电子这事称为“quantum effect”。quantum theory指的是波尔的电子运动角动量量子化、能级、跃迁、（爱因斯坦的）光子概念，还有新量子论（海森堡、薛定谔、狄拉克的波函数、其特征值对应的能量量子化、跃迁、光子概念。

电子是一个一个的，还有质子、中子是一个一个的，原子、分子是一个一个的，这些都不是quantum effect 。那些把油滴很小所以带一个电子也能测出（例如密立根油滴实验）电荷变化的事称为quantum effect的，是在碰瓷quantum这个“高档”词汇。

主要是confinement之后，能级变成离散的了，quantum dot又叫人造原子。

[TheMatrix]

Abstract
Manipulation of solid-state spin coherence is an important paradigm for quantum information processing. Current systems either operate at very low temperatures or are difficult to scale up. Developing low-cost, scalable materials whose spins can be coherently manipulated at room temperature is thus highly attractive for a sustainable future of quantum information science. Here we report ambient-condition all-optical initialization, manipulation and readout of hole spins in an ensemble of solution-grown CsPbBr3 perovskite quantum dots with a single hole in each dot. The hole spins are initialized by sub-picosecond electron scavenging following circularly polarized femtosecond-pulse excitation. A transverse magnetic field induces spin precession, and a second off-resonance femtosecond-pulse coherently rotates hole spins via strong light–matter interaction. These operations accomplish near-complete quantum-state control, with a coherent rotation angle close to the π radian, of hole spins at room temperature.