“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 (ms) 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 (ms).
It
is these Spin Quantum Number (ms) 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 (ms), 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 (ms).
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 (ms).
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.
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