University of @Princeton's Quantum Dot Maser is built for a Quantum Telecom Network

“In this paper the researchers dig down deep into the fundamental interaction between light and the moving electron. The double Quantum Dot allows them full control over the motion of even a single electron, and in return they show how the coherent microwave field is created and amplified. Learning to control these fundamental light­matter interaction processes will help in the future development of light sources”

Princeton's Eugene Higgins Professor of Electrical Engineering Claire Gmachl, a pioneer in the field of semiconductor Lasers, commenting on the developement of the double-Quantum Dot Maser by Quantum Entanglement by a University of Princeton Research Team

Lasers just seem to be getting smaller and smaller it seems!

Researchers at the University of Princeton have developed a Maser or Microwave Laser that is made of entangled pairs of Quantum Dots as reported in the article “Rice­sized Laser, powered one electron at a time, bodes well for Quantum computing”, published January 15 2015, Phys.org. 

Their research, published in the Journal Science, was led by Associate Professor Dr Jason Petta, who led a merry band of researchers so long, I have to do a list:

1.      Dr. Jacob Taylor, adjunct assistant Professor at the Joint Quantum Institute. University of Maryland­National Institute of Standards and Technology

2.      Mr Jiri Stehlik, a physics graduate student in Petta's lab

3.      Associate Research Scholar Christopher Eichler in Princeton's Department of Physics

4.      Postdoctoral Researcher Michael Gullans of the Joint Quantum Institute

5.      Mrs Yinyu Liu, a physics graduate student in Petta's lab

In so doing, they also achieved another first; demonstrated Quantum entanglement between pairs of Quantum Dots at a distance never seen with a very low powered variable frequency Laser. This has implications not only for Quantum computing and the development of Quantum Networks but more immediate application in improving Fiber Optic Telecommunications as well.

University of Princeton Quantum Dot Maser – How they got Quantum entangled in their work

Typical of scientists, building a Maser wasn't the original aim of their research, as they were really trying to figure out how to use Quantum Dots as Qubits in a Quantum computer.

But it still demonstrates what is possible with entangle Quantum Dots and may even have applications for telecommunications and even Quantum Dot LCD LED Displays, being a their Quantum Dot Maser has a frequency that can be adjusted to quote Dr. Jason Taylor: “I consider this to be a really important result for our long­term goal, which is entanglement between Quantum bits in semiconductor­based devices”.

This discovery, I admit, is a lot more interesting, as it implies that Quantum Dots can experience Quantum entanglement thought interacting via photons over distances greater than previously thought.

Thus they partially achieved a step towards their original goal by demonstrating that Quantum Dots can become Quantum entangled, effectively ending up in the same Quantum mechanical state and thereby communicating with each other, to quote Mrs Yinyu Liu, a physics graduate student in Petta's lab: “The goal was to get the double Quantum Dots to communicate with each other”.

To me personally, as a Part-time student doing the Professional Diploma in Teaching at the MICO College University, this is an astounding breakthrough, as I had always though Quantum Dots were just hyper-reactive clumps of atoms-outside of a macromoleculer structure.

I had no idea that they could exhibit Quantum entanglement, albeit I had always known that they could produce radiation once excited by an energy source i.e. light, heat, etc. In fact, the phenomenon of bio-luminiscence, photo-luminiscence and flourescence have been recently discovered to be cause by Quantum Dots, even in living organisms.

So how did the University of Princeton Research team create this Maser? First, a quick Primer on Quantum Computers and Quantum Dots.

University of Princeton's Quantum Dot Maser - Quantum computers and Quantum Dots explained

Quantum computers are basically regular computer that process binary (Base 2) data i.e. 1 (on) and 0 (off) using Qubits. A Quantum computer represents these Binary using the Spin Quantum Number (m_s) from the Qubits as explained in extreme detail in my blog article entitled “Kavli Institute of Nanoscience demonstrates Quantum Teleportation – Super-cooled Diamonds demonstrate faster-than-light potential for Computing and Telecommunications”.

Using Carbon atoms as an example, their Quantum numbers read as 1s², 2s² 2p².  You can have up to eight (8) Quantum States, with each of the six (6) electrons having an up or down spin state as denoted by the Spin Quantum Number (m_s).  

It is these Spin Quantum Number (m_s) that are read. Because a single Carbon can represent multiple bits, it is referred to as a Qubit.

Why Human beings stick to this convention even in the Quantum world is a mystery to me, as hexadecimal (Base 16) can work just as well, given the scale of atoms. At that size and given the fact that a single Carbon atom can have electrons exhibiting multiple Spin Quantum Number (m_s), individual Carbon atoms could represents bytes, not just bits, making Hexadecimal Quantum Computers a reality.

However, due to difficulty accessing the inner 1s electrons of the Carbon atom, the outer shell 2s² 2p² are usually used to represent the four (4) binary bits or the up and down states of the Spin Quantum Number (m_s).

Still, reading and writing data to a Quantum bit or Qubit represented by Carbon atoms is very hard, as they're prone to random movement due to energy from the environment causing them to vibrate.

So normally, experiments relating to Quantum computing are performed at near to absolute zero temperatures. In the experiments carried out by the University of Princeton researchers, they used such small clumps of atoms, usually 20 to 200, called a Quantum Dot.

This is because that many atoms in one place by themselves separate from a macro-molecular structure exhibit strange behavior, such as bio-luminiscence, photo-luminiscence, fluorescence. They are also highly reactive, being they’re not part of a more stable macromolecular structure stabilized by covalent or metallic bonds.

Their higher level of reactivity means that they can be used in a host of applications, from Quantum computing to LED LCD. Quantum Dots are the basis behind the Samsung Quantum Dot SUHD (Ultra High Definition Televisions) launched in January 2015 at CES (Computer Electronics Show) 2015 as described in my Geezam blog article entitled “Samsung's SUHD Smart TV Runing Tizen OS as UHD Alliance grows and Internet of Things beckons”.

University of Princeton's Quantum Dot Maser - How to get Quantum Dot Entangled and built and build an Electron-Maser

For their research the Researchers at the University of Princeton designed double Quantum Dots using a 50 nanometer thick wire made from a semiconductor material called indium arsenide.

They then ran the 50 nanometer thick indium arsenide wire between two (2) electrodes labeled S and D and arranged even thinner metal wires perpendicular to the indium arsenide wire.

These wires acted as a kind of magnetic gate to restrict the amount of electrons that could flow along the wire to one electron at a time to quote Associate Professor Dr Jason Petta:“They are forced to cross the stream one at a time. These double Quantum Dots are zero­dimensional as far as the electrons are concerned—they are trapped in all three spatial dimensions”.

In addition, the material that was used to make the Quantum Dots resulted in them being able to transfer only one electron at a time.

Finally, they fabricated two of these 50 nanometer thick wire Quantum Dot and spaced them apart by 6 mm inside of a tube made of a metal called niobium at a temperature of -459 F(-272.77 C) at which point it became a superconductor.

At each end of the niobium tube was reflective mirror, with one mirror being half-silvered and thus the point from which any radiation generated would emerge, the typical configuration of a Laser.

When the power was turned on, because of the presence of the supporting nanowires below the 50 nanometer wires that held the two (2) Quantum Dots, it resulted in only one electron at a time passing from one Quantum Dot to another.

As this one electron made the transition across the 50 nanometer wired from one Quantum Dot to the other along the bridge, it fell from a higher energy level to a lower energy level, somewhat like a boulder rolling down a hill.

It thus generated a wavelength of radiation equivalent to the difference in energy levels between the two (2) Quantum Dots cause by the one electron current, which is less than 1 billionth of the current used to power a hair dryer.

Because of the band gap between the energy levels of the Quantum Dots, that Quantum of radiation had a frequency equivalent to microwave radiation. Thus, the niobium Laser was really a Laser, with the added benefit being that the frequency of the radiation can be adjusted by changing the band gap energy between the Quantum Dots, much different from semiconductors Lasers or Masers whose frequency output is fixed during manufacturing.

But the exciting bit is that the microwave radiation generated by one pair of Quantum Dots cause the other pair of Quantum Dots to also display the same exact Quantum state in terms of their Spin Quantum Number (m_s).

Both pairs of Quantum Dots thus generated microwave radiation that was coherent and as it travelled up and down the niobium cavity, it reflected off the silvered walls at each end of the cavity, further exiting more atoms in the Quantum Dots.

The runaway effect generated a beam of coherent microwave energy, which emerged from one end of the half silvered mirrors, becoming the first Maser generated by entangled double Quantum Dots, to quote Dr. Jacob Taylor: “This is the first time that the team at Princeton has demonstrated that there is a connection between two double Quantum Dots separated by nearly a centimeter, a substantial distance”.

Quantum-Dot Maser – From Telecoms Applications to Quantum Computer future

Practical uses for this Maser include an alternative more efficient source for Microwave antennas and even FSO (Free Space Optical) and FLORA (Fiberless Optical Receiver Array) Networks. Quantum Dot LCD LED Displays are the more immediate applications, with the variability in frequency making it possible to create super thin, even transparent HDTV 4K Displays.

It can even be used to develop Optical Computers where all data is transmitted and received as beams of laser light as predicted in my blog article entitled “Fiber Optic Thunderbolt Cables are coming by the Third Quarter of 2013 – Apple Mac's to finally get upgraded as Optical Computer now closer to practicality”. Soon, Quantum Switched Optical Networks will make high speed Optical computers for home users using FTTH (Fiber to the House) a reality.

Room Temperature semiconductors composed of Group 4 Element in the Periodic Table such as graphene or silicene as explained in my blog article entitled “@UTAustin at Austin develops Silicene Transistors - How to grow Silicene and Group 4 Super-conducting Processors and Batteries on Silver Spoon” could be used as the evacuated Tunnel, making room Temperature Quantum computers possible.

So the University of Princeton not only created possibly the most efficient Maser on planet earth, but they managed to demonstrate Quantum entanglement at distance previously though impossible.

Hopefully, the next time they publish, they'd have developed a Quantum Computer, preferably working at room temperature using room temperature semiconductors.