Quantum Quest
Introduction
In the last centuries, every physical theory have spawn new technologies, from the understanding of velocities and masses we had the development of mechanical systems; from thermodynamics the development of thermal engines; while the understanding of electricity and magnetism lead to the development of electrical circuits, washing machines and modern telecommunication and computation industries.
Similarly, the last great physical revolution occurred in the XX century, the understanding of the atomic and subatomic world driven by quantum physics, is now leading to the development of a whole new class of technologies, what we now call quantum technologies. These new technologies promise to revolutionize our world improving everyday tasks like communications, sensing, simulations and computations. However, to engineer these futuristic technologies, our labs and industries need to master the art of controlling single atoms and to manipulate them to create specific states characterized by unique quantum properties, known as entanglement. This is the quest ahead of us, already undertaken by many researchers and innovators around the world that this game is representing.
Join us in the challenge of developing quantum technologies, increase your research capability, create thousands of qubits and entangle them faster than your adversaries, be the first to climb the pyramid of quantum technology and claim your space in the history of science and technology!
Resources
Qubits
The qubits are the elementary bricks used to build quantum technologies. In modern ICT, bits are used to encode information and to perform communication and computation tasks. In quantum technologies qubits brings quantum information and can be implemented with different hardware: single atoms or ions, superconducting circuits, single photons or even impurities in diamonds. Qubits are necessary to build all quantum technologies: they encode quantum information and can be manipulated to transfer messages, perform computations and simulations, or to perform measurements with better performances than with any classical technology currently in use.
Entanglement
Entanglement is a unique property of quantum systems, what distinguish a quantum system from a classical one. What has been theoretically proven and later on experimentally demonstrated, is that two quantum systems can be correlated in a way stronger than any classical system can be. Correlations means that one system state depends on the other system state, that is, that one system knows something about the other. Thus, correlated systems can be used to process and transmit information, the more correlated the more efficient the protocol can be. Given that quantum systems can be more correlated than classical ones, those information protocols can be more efficient than classical ones, leading to better and more performing technologies.
Entanglement, these very strong correlations, is possible to establish only between quantum systems. It is extremely difficult to increase the number of systems (e.g., atoms) that are entangled, as more atoms you consider the more the system becomes classical (we are classical systems made of trillions of atoms), and by definition classical systems do not display quantum behavior. Entanglement is one of the quantum mechanical properties that made Einstein disbelief the correctness of quantum mechanics.
Research & Development capability
Every human endeavor requires resources, planning, efforts and endurance, hopefully helped by some luck: as they say, “Rome wasn’t built in a day”. This is particularly true with fundamental research and high-tech development. The only successful way we know to trigger and maintain constant development of fundamental research and advanced technologies is to create and maintain for long time an environment where the many necessary components to make research and development thrive can meet: high-skilled human resources trained in a stable and fully developed system of Universities and public and private research centers; availability of funds at different levels (steady long-term for fundamental research, mid-term investments for technology developments and high-risk high-gain capital for industrial developments); infrastructures encompassing from strategic communications to high-level enabling technologies; easy access to all necessary previous know-how and high-technologies to be exploited to develop the next step. In summary, to be able to produce the mix that resulted in decades of leadership in some specific high-tech, such as, e.g., the Silicon Valley for the world wide web and dot companies.
Quantum eras and entanglement levels
This game represents the quest for developing quantum technologies. This is represented by the pyramid to be build, formed by four different eras. The first and starting one, represents the foundations that made all this possible.
In the Foundational era (ERA 0), entanglement is a bare theoretical idea not yet well understood, triggering profound scientific and philosophical discussions on its mere existence. This theoretical, fundamental and apparently useless research lead the foundations for all the technology developed today, based on the quantum mechanical physical laws and the consequent understanding of the atomic structure and of the property of superconductors, the theory of quantum information, and the laser technology.
The next era (ERA 1) represents the development of the quantum information theory and of the first experimental demonstrations, where the existence of entanglement and of its properties have been experimentally proved. The first one- two-qubit systems have been built in the labs and have been entangled.
The following era represents the current period (ERA 2), where nontrivial quantum information protocols have been experimentally demonstrated, some of them are leaving the labs and are being engineered by commercial companies, creating new markets and novel possibilities. The main limitations faced by all these technologies is the ability of entangling more than some tens of qubits, necessary to fully exploit their potential.
Finally, the last era (ERA 3), represents a foreseeable future where quantum technologies have been fully developed and engineered, and will impact all information and communication technology aspects of our life. Our ability of creating and manipulating entangled qubits will be beyond hundreds of them, enabling fault tolerant quantum computation and the implementation and exploitation of all theoretical quantum information protocols proposed so far.
Quantum technologies pillars
Quantum technologies can be classified in four large areas or main pillars, as done by the Quantum Flagship, the first continental funding program funded by the European Union to develop quantum technologies in this decade (www.qt.eu). These pillars are Quantum Computation, Quantum Simulations, Quantum Communications and Quantum Sensors, each of them devoted to developing the specific quantum version of the corresponding classical ones. In the Quantum Quest game, each card is characterized by one or more symbol (put symbols here below?) depending if it represents a scientific result that belongs to one or more pillars. Each specific pillar gives a corresponding advantage to the player that plays that card.
Cards
ERA 0 – Foundations – Entanglement level 0
Schrödinger Equation: the fundamental quantum physics law describing the world of atomic and subatomic particles. First proposed in 1925 by Erwin Schrödinger, one century later is at the earth of our understating of quantum technologies.
Theory of information:
Established in the 40s by Claude Shannon, it defined the concept of information in quantitative terms, introduced the concept of bit of information (a system with two possible different states, 0 and 1) and how to measure how much information is stored, produced and transmitted.
Einstein-Podolsky-Rosen paradox: A famous paradox proposed by Albert Einstein and colleagues that was a logical consequence of the laws of quantum physics. Quantum systems could be “entangled” displaying unintuitive properties, become famous as “spooky action at distance”. The experiment at the time was considered impossible to perform in the lab but anyway triggered profound discussions on the very nature of our universe.
Atom physics: once the fundamental laws of quantum have been unveiled, the properties of atoms have been studied and understood, correctly interpreting experimental observations: atoms emission and absorption spectra, interaction with electromagnetic fields, interactions between atoms.
Theory of superconductors:
From the laws of quantum mechanics it has been possible to understand the peculiar behavior of some materials that, below a critical temperature, become perfect conductors, with zero resistance to passing currents. This allows, for example, to have an infinitively lived current in a ring of metal or sending electrical signals with an enormous spare of energy.
Transistor:
A landmark development of classical circuitry that enabled the following developments and miniaturization of classical circuits and electronic chips, present in every modern technology, from computers to mobile phones, from washing machines to cars.
Laser: A consequence of the quantum nature of light, we mastered the art of creating coherent light where every photon behaves in the very same way, differently from natural light where each photon is slightly different. The net result are laser that enabled many different technologies like laser pointers, compact disks, lithography etc.
ERA 1 – Quantum Information – Entanglement level 1
Heisenberg limit: the theoretical proof that entanglement enables measurement protocols that outperforms classical measures is put forward and protocols to probe it in the lab are proposed.
Interaction-free measurement:
A theoretical protocol that exploits the superposition and measurement postulates of quantum mechanics is put forward: it shows that theoretically it is possible to learn if an object is present in a particular place without looking or interacting with it.
NV-centers in diamonds: the quantum properties of defects in diamonds at room temperature are investigated and established. They are individuated as potential qubits for quantum information processing that could work at room temperature.
Bell’s inequalities: In 1964 John Bell proposed the first experiment to test in the lab the Einstein-Podolsky-Rosen paradox: A particular combination of measurements on two photons prepared in a special (entangled) state, could determine if quantum mechanics is correct or not.
Aspect’s experiments: In 1982, Alain Aspect, Philippe Grangier and Gérard Roger, performed the first solid experimental test of Bell inequalities, proving that quantum entanglement is real and quantum mechanics describes entanglement and other counterintuitive properties of nature correctly.
Quantum Key Distribution:
John Bennet and Gilles Brassard proposed in 1984 a protocol (BB84 protocol) to distribute cryptographic keys in a secure way exploiting quantum properties of photons. In such a way, encryption security is ensured by the quantum laws of nature and is inherently secure.
Feynman’s conjecture:
In 1982, Richard Feynman conjectures that a computer built with quantum systems, a quantum computer, would be much more powerful than classical ones in solving certain exponential hard tasks, like the simulation of high-energy physics problems.
Lloyd’s proof of Feynman’s conjecture:
In 1996, Seth Lloyd proves Feynman’s conjecture showing that a universal quantum computer could efficiently simulate complex quantum systems like large molecules, different materials or quantum chromodynamics.
Atoms in optical lattices:
The ability of trapping individual atoms by means of lasers in variable patterns enables the quantum simulation of different materials, of their different phases of matter and their electronic, magnetic or topological properties, and of the quantum phase transition among them.
Grover’s algorithm:
One of the first quantum algorithms that demonstrated the potential advantage of quantum computers. Searching in an unstructured database with quantum computers is faster than with classical ones, with a quadratic speedup with respect to the database size.
Quantum Fourier Transform:
Most information processing is performed via a ubiquitous mathematical operation, the Fourier Transform. Quantum computers can perform this transformation exponentially faster than classical ones, serving as efficient subroutine for many other quantum algorithms.
Shor’s algorithm: One of the most famous quantum algorithms, introduced by Peter Shor in 1994. It shows that universal quantum computers could break the current Rivest-Shamir-Adleman (RSA) cryptographic standard, potentially menacing the current telecommunications infrastructure.
Trapped ions two-qubits gate: The first experimental demonstration of a logical operation between two ion-qubits is performed, following the theoretical proposal of Ignacio Cirac and Peter Zoller in 1995.
Rydberg atoms in optical tweezers: atoms excited to very high orbitals preserve their quantum properties for very long times, while becoming of sizes of the order of micrometers. This creates the perfect conditions to trap them via special lasers called optical tweezer and to engineer a quantum computing hardware.
Superconducting qubits: the first experimental demonstration of a two qubits gate between superconducting qubits is performed in 2003 at the RIKEN-NEC labs in Japan.
Boson sampling: a particular mathematical problem (how to predict where a photon will end up in a particular combination of coupled optical fibers) is proposed as a suitable candidate for demonstrating the quantum advantage in photonic quantum computing hardware with limited resources.
Teleportation: a fascinating quantum protocol that enables transferring the state of a qubit from one to another exploiting the entanglement with an intermediate one. It is at the base of many quantum communication protocols and has been demonstrated first demonstrated in 1997 by the group of Anton Zeilinger in Vienna.
Quantum random numbers:
quantum superposition properties can be exploited to engineer a generator of true random numbers. Having true random numbers enables many important applications in science, security and cryptographic protocols, and games (lotteries and online card games).
Topological entanglement:
Intimate relations between topological order, a particular class of state of matter that depends only on global properties and cannot be changed by local perturbations, and entanglement is unveiled.
Quantum optimal control:
optimal control theory is a branch of mathematics that allows to engineer algorithms at the base of robotic movements, self-guiding cars and most modern automated technologies. Its extension to the quantum realm is now at the heart of most complex quantum hardware, e.g., enabling a precise manipulation and control of single atoms by laser fields.
Tensor network methods:
A powerful classical numerical methods that allows simulations of large scale many-body quantum systems and the development of digital twins of complex quantum technologies, boosting their engineering and development.
Entanglement theory:
the theory of entanglement is developed unveiling its profound connections, for example, with information theory, measurement theory, phase transitions and topology.
Post-quantum cryptography:
New classical cryptographic protocols are developed to replace the current standard RSA protocol, in case quantum computers development will start to allow potential quantum attack to the current encrypted communication infrastructures.
No cloning theorem: In 1982 it was proven that a quantum system cannot be photocopied as we do with classical ones! No quantum machine or protocol can perfect copy a quantum system without disturbing (or even destroying it as in the teleportation protocol!) the original one. This quantum feature is at the heart of QKD security.
ERA II – Noisy-Intermediate scale quantum (NISQ) – Entanglement level 10
Magneto quantum sensors: quantum bits are integrated to create a sensor that can be used to measure magnetic fields with very high precision.
Brain sensors: NV-centers in diamonds are applied for sensing neuron activities from outside the brain, without the need of inserting microneedles. Their sensitivity and being biological inert make these sensors highly promising for biomedical applications.
Satellite for quantum communications: the first satellite implementing quantum communication protocols is launched in orbit and proven to be functional.
Long-distance Quantum Key distribution: quantum key distribution is proven to be functional over hundreds of kilometers in telecom optical fibers and in free space in natural conditions, also in presence of turbulence and not perfect conditions.
Quantum chemistry simulation: proof-of-principle quantum simulations of chemistry problems are performed on different quantum computing and simulation hardware.
Quantum electrodynamics simulations:
heading towards the realization of Feynman’s seminal idea, proof-of-principle quantum simulations of high-energy physics problems are performed on different quantum computing and simulation hardware.
Quantum advantage experiments: the first experiments claiming to have performed a quantum computation beyond the capabilities of any classical supercomputer starts to appear. The claims are debated within the scientific community, but clearly show a general trend toward the ability of performing increasingly complex quantum computation.
Quantum machine learning: the idea of exploiting quantum computer to perform machine learning tasks is put forward and explored, showing a potential quantum advantage also in the ubiquitous applications of machine learning.
Atom-based quantum hardware: commercial quantum computer hardware based on neutral atoms is developed and proven to be working on proof of principle mid-scale quantum computation.
Superconducting hardware: commercial quantum computer hardware based superconducting circuits is developed and proven to be working on proof of principle mid-scale quantum computation.
Ion-trap hardware: commercial quantum computer hardware based on trapped ions is developed and proven to be working on proof of principle mid-scale quantum computation.
Quantum repeaters: a quantum protocol developed to create entangled particle at long distances is experimentally proven over hundreds of kilometers.
Integrated photonics:
the laser fields driving the quantum computation are brought to the quantum bits via integrated optical fibers, resulting in more performant, stable and versatile quantum chips.
Quantum venture capital: venture capital start to invest on startups promising to develop various quantum technologies, providing the necessary risk capital to foster a rapidly growing economic system of new companies, complementing the public investments in the basic research driven by Universities and Research centers.
ERA III – Quantum ERA – – Entanglement level 100 and beyond
Quantum scanners: quantum sensors are used to develop quantum scanners able to exploit entanglement and superposition to enhance their performances.
Quantum-based diagnostic:
quantum scanners are exploited in the medical diagnostic enhancing the quality and precision of imaging tools and facilitating acquiring vital information in non-invasive ways.
Quantum internet: quantum computers are connected via quantum communication channels obtaining an integrated and secure network of quantum processors with unprecedented computational power.
Quantum-Classical R&D: quantum Computers are interfaced with High-Performance Computing Centers around the world and exploited as computing coprocessors. They become a standard part of the R&D process drastically enhancing the world basic and applied research processes.
Quantum engineered drugs: quantum computers are exploited to efficiently simulate drug and molecular processes enormously speeding up the drug development while drastically reducing their development costs.
Quantum secure communications: quantum cryptography is adopted as a world standard and deployed in commercial, defense and critical environment ensuring secure communications certified by the quantum properties of photons.
Quantum machine learning: universal quantum computes are applied to machine learning tasks boosting the current capabilities, drastically reducing the time and energy needed for AI applications.
Quantum Blockchain: universal quantum computers and quantum communications are integrated to develop blockchains with quantum-secure standards.
Universal Quantum Computation: quantum computers are able to run large scale complex quantum algorithms realizing any thinkable quantum algorithms. Feynman’s conjecture is realized in labs and supercomputing centers around the world and a new computation era begins.
Quantum engineered materials: universal quantum computers are routinely used to engineer new materials with the desired characteristics needed to amplify quantum technologies performances in terms of precision, energy needs and speed.
Acknowledgments
We acknowledge support from the Quantum Computing and Simulation Center of Padova University via the World Class Research Infrastructure grant and of the Department of Physics and Astronomy of Padova University. We thank the inspiration, testing capabilities, graphical inspiration and support, and comments of Pietro Silvi, Ilaria Siloi, Marco di Liberto, Carmelo Mordini, Marco Ballarin, Timo Felser.