Quantum Discrimination for Data Retrieval (qDATA)

Information is very important in our society. It is the "thing" which is processed by our computers and transmitted over the Internet. Every day we enjoy its benefits, since acquiring information means increasing our knowledge. For this reason, storing information is also very important. This is a process which is very common in our routine lives; for instance, think of a hard disk working in the background, or a DVD burned as a back-up of your most important data.

Advances in data storage could be much greater if they came from a deeper understanding of the concept of information. The basic unit of information, the bit, relies on our ability to distinguish between two states of a physical system. At the quantum level, storing and retrieving a bit of information relies on the capacity to discriminate between two quantum states of the system, e.g., spin up or spin down of an electron.

In our proposal, we consider a more advanced approach where information is encoded using quantum channels, i.e., the most general physical maps between quantum states. In our model, an encoder randomly picks a quantum channel from a pre-established ensemble, labeled by a classical variable. This channel is then stored in a black box and passed to a decoder. To identify the channel and retrieve the value of the variable, the decoder uses a transmitter, for feeding an input state into the box, and a receiver, for measuring the possible output states. Thus, data is stored in an ensemble of quantum channels and retrieved by the process of quantum channel discrimination.

Motivated by this approach, our first aim is to solve the general problem of quantum channel discrimination, by considering ensembles of Gaussian channels and assuming decoders with limited energy. This is an open problem, whose optimal solution will provide the core for a general theory on Gaussian channel discrimination.

This theory will then be applied to practical scenarios which are important for data storage. We will consider the quantum reading of digital memories, where the use of faint quantum light is remarkably efficient in retrieving data from classical optical discs (resembling CDs and DVDs). Our aim is to optimize this model by including error correcting codes and, most importantly, to make it practical by studying all the details of its optical implementation, where the inevitable presence of diffraction causes effects of inter-bit interference. Thanks to this study, we will be able to promote this theoretical idea to the level of a technological prototype, ready to be experimentally implemented.

The field implementation of a quantum reader could be a breakthrough in data storage, since we could increase data transfer rates and storage capacities of our digital memories by orders of magnitude. Furthermore, thanks to the non-invasive nature of the quantum light, new photo-degradable materials could be used by the industry for the construction of new types of organic memories. Our approach is high-risk but it could open the way to radically new forms of information technologies.

Then, a generalization of quantum reading is quantum pattern recognition. Here we aim to prove how quantum correlations can dramatically improve the performances of pattern matching in supervised and unsupervised algorithms (for instance, for data clustering). Quantum pattern recognition can potentially lead to a dramatic boost in the classification of raw data with minimal use of energy, negligible error rates and fast acquisition times. This technique could be used for the probing of very fragile biological or human samples in order to recognize the presence of bacterial growths or cancerous cells. Thanks to its non-invasive nature, quantum light could also be used for a continuous real-time probing of such samples. Results could be revolutionary in the long-term, providing completely new techniques for biological analysis and medical imaging.

The potential non-academic beneficiaries of this research can be divided in three main groups:

1) Society (Computers, Networks, Hospitals)

Today, quality of life is based on how fast and reliably computers are able to manipulate information, and data storage represents an important step in this process: faster and greater capacity memories are indeed necessary for realizing faster and more powerful computers and communication networks. Quantum reading is an effort in this direction: some of the most fundamental resources in nature (quantum correlations) are exploited to greatly improve the performances of an important information task, as the readout of data from digital memories.

An evolution of quantum reading is quantum pattern recognition, which aims to identify data with the minimal use of energy. A remarkable future application could be the probing of very fragile biological systems or human samples in order to recognize hidden patterns, e.g., bacterial growths or cancerous cells. Specific patterns of concentration could easily be spotted by using non-invasive quantum light, whereas classical light would just be useless or would destroy the samples. Thanks to its non-invasive nature, quantum light could also be used for a continuous real-time probing of these fragile samples. Such applications could provide important future techniques of medical imaging for private and public hospitals, with consequent benefit for the welfare of our society.

Note that the potential use of quantum mechanics to improve medical devices is currently a very hot topic in the US and Canada. Mike Lazaridis (inventor of the BlackBerry smartphone) has just opened the "Mike & Ophelia Lazaridis Quantum-Nano Centre" in Waterloo (Ontario) financing the effort with a $100 million donation. The development of noninvasive medical-testing equipment based on quantum technology will be the main focus of the fund (for more details see the article: http://www.bloomberg.com/news/2013-03-19/blackberry-inventor-starts-fund-to-make-star-trek-device-reality.html).

Impact is long-term (10-30 years).

2) Economy (Industry, Defence)

Our research on quantum reading could generate radically new forms of data storage and information technology with a long-term impact on the UK economy in terms of new companies and wealth creation. Potentially, we could speed up the readout of optical digital memories (e.g., DVDs and Blu-Rays) by orders of magnitude, as well as dramatically increase their storage capacities. New materials could be exploited for constructing organic memories, thanks to the non-invasive nature of the quantum light employed by these future devices.

Quantum pattern recognition could dramatically boost the classification of unknown data, with no error and ultrafast acquisition times. Confidential data could be encoded in patterns which are recognizable only by specifically-designed sources of quantum light. Applications are therefore for our Defence and private companies working in security and cryptography.

Impact is long-term (10-30 years).

3) Knowledge (General Public, Schools)

The general public is very interested in how science could have a revolutionary impact on technology. Therefore, connecting a difficult fundamental field, as quantum physics, to practical information tasks, such as the readout of optical discs, will foster increased interest by the public for basic science and research in general.

The specific outcomes of the present project and the physical principles behind it could be used as an educational tool by high-school teachers to promote student interest in basic science. Middle-schools students could also be interested in such applications of quantum information and consider a future career in this basic science on the basis of its technological impact.

Impact is short-term (1-3 years).