System Bits: May 19

Foundation for quantum computer
In theory, quantum computers are capable of simulating the interactions of molecules at a level of detail far beyond the capabilities of even the largest supercomputers today, which are expected to revolutionize chemistry, biology and materials science. However, the development of quantum computers has been limited by the ability to increase the number of quantum bits, or qubits, that encode, store and access large amounts of data.

Now, researchers at the Georgia Tech Research Institute (GTRI) and Honeywell International have demonstrated a device that allows more electrodes to be placed on a chip, which they say is an important step that could help increase qubit densities and move technology one step closer to a quantum computer that can simulate molecules or perform other algorithms of interest.

The lead researcher explained that to write down the quantum state of a system of just 300 qubits, approximately 2^300 numbers are needed, which is roughly the number of protons in the known universe. As such, no amount of Moore’s Law scaling will ever make it possible for a classical computer to process that many numbers.

This is why it’s impossible to fully simulate even a modest sized quantum system, let alone something like chemistry of complex molecules, unless a quantum computer can be built to do it.

While existing computers use classical bits of information, quantum computers use “quantum bits” or qubits to store information. One leading qubit candidate is individual ions trapped inside a vacuum chamber and manipulated with lasers. The scalability of current trap architectures is limited since the connections for the electrodes needed to generate the trapping fields come at the edge of the chip, and their number are therefore limited by the chip perimeter.

The GTRI/Honeywell approach uses new microfabrication techniques that allow more electrodes to fit onto the chip while preserving the laser access needed, similar to a ball grid array.

Photograph and SEM images of the gold studs attached to the interposer—these form the “ball bonds” used to connect the trap and interposer chips. (Source: Georgia Institute of Technology and Honeywell)

The researchers noted that while much much work remains to be done to shrink the technology, the advances they’ve developed such as the microfabrication techniques are also relevant for making miniature atomic devices like sensors, magnetometers and chip-scale atomic clocks.

Implantable devices last longer with optimal size, shape
Less than the material they are made of, researchers at MIT have discovered that biomedical devices made in a certain size and shape can last longer in the body by creating less of an immune-system rejection response.

Although the researchers expected that smaller devices might be better able to evade the immune system, they discovered that larger spherical devices are actually better able to maintain their function and avoid scar-tissue buildup. They were surprised by how much the size and shape of an implant can affect its triggering of an immune response. What it’s made of is still an important piece of the puzzle, but it turns out if you really want to have the least amount of scar tissue you need to pick the right size and shape.

The researchers said they hope to use this insight to further develop an implantable device that could mimic the function of the pancreas, potentially offering a long-term treatment for diabetes patients. It could also be applicable to devices used to treat many other diseases.

The researchers tested spheres in two sizes — 0.5 and 1.5 millimeters in diameter. The devices prepared with the smaller spheres were completely surrounded by scar tissue and failed after about a month, while the larger ones were not rejected and continued to function for more than six months.

The larger spheres also evaded the immune response in tests in nonhuman primates. Smaller spheres implanted under the skin were engulfed by scar tissue after only two weeks, while the larger ones remained clear for up to four weeks. They observed over an order of magnitude fewer immune cells on all surfaces of larger diameter spheres.

The sugar polymers that make up the spheres in this image are designed to package and protect specially engineered cells that work to produce drugs and fight disease. While on-site, they must remain undetected by the body’s natural defense system. However, the reddish markers on the spheres’ surfaces indicate that immune cells (blue/green) have discovered these invaders and begun to block them off from the rest of the body. Further experiments with the spheres’ geometry and chemistry will lead to better invisibility cloaking and longer lasting protection for these cell-based factories. (Source: MIT)

The researchers believe this finding could be applicable to any other type of implantable device, including drug-delivery vehicles and sensors for glucose and insulin, which could also help improve diabetes treatment. Optimizing particle size and shape could also help guide scientists in developing other types of implantable cells for treating diseases other than diabetes.

Smartphone video microscope
In it’s next generation CellScope technology, UC Berkeley engineering researchers have developed a new smartphone microscope that uses video to automatically detect and quantify infection by parasitic worms in a drop of blood that they believe could help revive efforts to eradicate debilitating filarial diseases in Africa by providing critical information to health providers in the field.

These researchers had previously shown that mobile phones can be used for microscopy, but this is the first device that combines the imaging technology with hardware and software automation to create a complete diagnostic solution.

The video CellScope provides accurate, fast results that enable health workers to make potentially life-saving treatment decisions in the field, they asserted.

The UC Berkeley team teamed up with Dr. Thomas Nutman from the National Institute of Allergy and Infectious Diseases, and collaborators from Cameroon and France to develop the device. They conducted a pilot study in Cameroon, where health officials have been battling the parasitic worm diseases onchocerciasis (river blindness) and lymphatic filariasis.

The video CellScope, which uses motion instead of molecular markers or fluorescent stains to detect the movement of worms, was as accurate as conventional screening methods, the researchers found.

A schematic of the CellScope Loa device, a mobile phone-based video microscope. The device includes a 3D-printed case housing simple optics, circuitry and controllers to help process the sample of blood. CellScope Loa can quantify levels of the Loa loa parasitic worm directly from whole blood in less than 3 minutes. (Source: Berkeley)