skip to main | skip to sidebar

Wednesday, May 11, 2011

Though they may not cut the mustard for a marriage proposal, flawed diamonds are ideal for maintaining quantum states. For the past few years scientists have found ways to influence and manipulate atoms near nitrogen-vacancy (NV) centers in flawed diamonds. These capabilities may someday make complex quantum computers or even a quantum internet a reality. 

So what exactly is quantum computing and how are quantum computers different than the run of the mill computers we already have? In a nutshell the difference lies in something called a quantum bit, or a qubit. A qubit is capable of maintaining a superposition of two states whereas classical bits are one state or the other, otherwise known as little ones and zeros. 

The key to understanding these processes lies in understanding the function of the NV center, one of the most common defects in diamond. As everyone knows a perfect diamond is made entirely of carbon; however, if nitrogen is introduced during formation it can become included as a defect.

Model of a Nitrogen Vacancy Center
Carbon alone would attach itself to 4 other carbon atoms; nitrogen however, bonds to only 3 carbon atoms creating the vacancy in the lattice structure where the 4th carbon atom would normally reside. This formation provides an electron free to move around the vacant space and around the neighboring atoms. The electron can then be coupled to the nuclear states of the surrounding carbon atoms and for the purpose of quantum computing they become entangled qubits. 

The problem with using the vacancy as a means for quantum computation is that it’s impractical to implant single nitrogen atoms one by one through a thin layer of diamond when you’d need several thousands in a single layer. In a study titled Chip-Scale Nanofabrication of Single Spins and Spin Arrays in Diamond, published in the July 23rd issue of Nano Letters, researchers described a method for mass-producing these NV centers, which may be fundamental in creating quantum networks. 

In the process researchers employed a thin layer of resist to cover the diamond. Through the resist they blast away using electron beam lithography. Next they shower the resist with nitrogen ions that end up going through the holes that were created in the top film layer. Once the nitrogen ions pass through the holes in the resist they embed themselves in the actual diamond creating the desired vacancies. Since the researchers were able to control the array of holes, they were able to control the array of vacancies. 

Thanks to these advancements it may now be possible to create vast networks of qubits, which someday may be lead to scalable quantum computers capable of complex problem solving. The next step to move forward in the quantum-computing race is for scientists to develop qubits that are able to hold their states for longer. This would provide processors with the means to run complex algorithms and perform practical problem solving. While diamonds are forever, unfortunately quantum states are not.

Saturday, May 7, 2011

Honeybees and Queen in Honeycomb
All female honeybees are created equal, until they’re 72 hours old that is. While still in the larvae state, the female honeybee (Apis melifera) has an uncertain fate. Though it is highly likely that she will become a worker bee, there is a slight chance that she will be destined for royalty. There are two female castes amongst honeybees: the worker (a sterile female), and the queen (a fertile female). It is impossible to differentiate genetically between worker bees and queen bees. So what makes a queen, a queen? 

Royal jelly, a substance secreted from the heads of worker bees, is fed to all bee larvae up to 72 hours. At that time larvae meant to be workers are switched to a diet of honey and pollen whilst the larvae fated for queendom continue on a strict royal jelly diet. It has been known for some time that royal jelly is the cause of the transformation from a normal female honeybee in the larvae state into a queen bee with increased size, reduced developmental time and enhanced ovary development; however, the specific mechanism has remained unknown. 

In a paper published by Japanese researchers in the April edition of Nature, evidence was presented that suggests Royalactin, a 57-kDa protein found in royal jelly, to be the cause of the queen bee’s superior development. Royalactin not only enhanced growth in the female honeybee but in fruit flies (Drosophila melanogaster) as well. Mechanistically the protein was found to promote queen development via an epidermal growth factor receptor (EGFR) mediated signaling pathway by activating and increasing the activity of mitogen-activated protein kinase, which was found responsible for promoting many queen like qualities. In the study researchers found the knocking down of EGFR expression in the bees and the fruit flies stifled the queen like superior development, showing that EGFR facilitates these processes. 

For years the royal jelly effect has fascinated humans. Though there hasn’t been much conclusive evidence regarding it's benefits for human application or consumption, royal jelly has found it’s place in several herbal remedies and beauty products. Perhaps royalactin will be the next big thing at health spas and beauty salons where human workers will be the ones providing the royal treatment.