In May, quantum computing was in the news as Google helped fund NASA's Quantum Artificial Intelligence Laboratory to house a D-Wave 2 quantum computer, by paying for the device. In a blog that I wrote at the time, I speculated that "I can imagine a validation system using a quantum computer that would avoid number-of-bits precision limitations during a simulation of an analog IC."
Like another possible game changer, silicon photonics, quantum computing is an appealing topic in part because of the unknown potential. In fact, there is enough interest that market forecasts are appearing for quantum computing. Research firm Research and Markets released a new report earlier this month, succinctly titled "Photonic Integrated Circuit (IC) & Quantum Computing Market (2012 - 2022): By Application (Optical Fiber Communication, Optical Fiber Sensors, Biomedical); Components (Lasers, Attenuators); Raw Materials (Silica on Silicon, Silicon on Insulator)."
The title alone is a mouthful, but in a press release, Research and Markets finds that "quantum computing is another application of PICs which is forecasted to be commercialized in 2017. This technology is expected to completely revolutionize the computing industry." PICs stands for Photonic Integrated Circuits, yet another hot topic in communications. Research and Markets estimates the total market for PICs will be more than $1.5 billion by 2022, growing at more than 26 percent a year between now and then.
The thing to keep in mind is that photons are the poster children for research in quantum states, quantum entanglement, and other unusual physics that may enable quantum computers. Thus, if you are forecasting a possible future where quantum computers are the workhorses, it makes sense to closely follow PICs and related technologies.
Quite a bit has happened since May. In that same month, Charles Margolis, writing on investor website Seeking Alpha, suggested that investing in quantum computing was fairly risky. The theme of Margolis's article was to explore any potential threat to companies like Intel, which might be presented by the evolution of quantum computing. He quoted an Intel source stating that Intel was not involved in quantum computing. Essentially this was all in response to the press about D-Wave at the time.
In June, physics.com reviewed quantum computing, devoting a lot of page space to the boson sampling devices I mentioned in my May blog. While they noted that boson sampling devices working on 20 to 30 photons are needed to fully see quantum interference effects, they also noted those barriers did not stop the formation of a $100 million (Canadian) private equity fund for quantum physics.
Just a few weeks later, Photonics Online reported on an MIT advancement in so-called "optical transistors." Although not essential for quantum computing per-se, a true optical transistor is considered key to a fully photonic computing scheme.
MIT's work had to do with creating a "cloud" of super-cooled atoms, which were initially transparent but were entangled. Quantum entanglement is another very non-intuitive quantum behavior in which two atoms or photons become matched in their quantum states (i.e., they are entangled), and remain so even when separated by relatively large distances.
This means that if you change the state of one entangled partner, the other also changes state, even though it is not close to the first partner. This allowed the MIT researchers to switch the state of the cloud with a single photon, changing the cloud from transparent to 80 percent opaque to light. Possibly the switching photons could then be sent around a PIC, switching photonic gates and leading to an actual photonic processor.
In early September, Bristol University in the United Kingdom announced Quantum in the Cloud, an interesting program wherein you can use a simulator of a boson sampling-like device to try out quantum computing experiments. Once you are ready for the real thing, you can register to use a 2-qubit quantum computer over the web.
Later in September, the University of California at Santa Barbara announced a new paper on Nature Physics Letters, describing a nanomechanical transducer device capable of converting electrical quantum states to optical quantum states. In the press release, the researchers say their device "uses an optomechanical crystal implemented in a piezoelectric material in a way that is compatible with superconducting qubits." The following figure shows a color-coded SEM (scanning electron micrograph) of the device.
Scanning electron micrograph of the device showing the mechanically suspended optomechanical crystal (blue) with electrodes (yellow) and the photonic circuit (red).
The UCSB team plans to eventually connect the device to super-cooled quantum devices. Andrew Cleland, an author of the UCSB paper and associate director of the California Nanosystems Institute at UCSB, is quoted in the press release, saying, "We believe that combining optomechanics with superconducting quantum devices will enable a new generation of on-chip quantum devices with unique capabilities."
What I believe is that creating qubits and entangled quantum states is becoming relatively common, and we may be entering an era of applications within a decade or so. As I said in May, such computing devices may be well suited to simulate and design analog systems, which inherently deal with continuous phenomena instead of digital ones.