One concept for planetary exploration involves using many small robotic landers that can cover more ground than a single conventional lander. In addressing this vision, NASA has been challenged in the National Nanotechnology Initiative to research the development of miniature robots built from nano-sized components. These robots have very significant challenges, such as mobility and communication, given the small size and limited power generation capability. The research presented here has been focused on developing a communications system that has the potential for providing ultra-low power communications for robots such as these. In this paper an optical communications technique that is based on transmitting recognizable sets of photons is presented. Previously pairs of photons that have an entangled quantum state have been shown to be recognizable in ambient light. The main drawback to utilizing entangled photons is that they can only be generated through a very energy inefficient nonlinear process. In this paper a new technique that generates sets of photons from pulsed sources is described and an experimental system demonstrating this technique is presented. This technique of generating photon sets from pulsed sources has the distinct advantage in that it is much more flexible and energy efficient, and is well suited to take advantage of the very high energy efficiencies that are possible when using nano scale sources. For these reasons the communication system presented in this paper is well suited for use in very small, low power landers and rovers. In this paper a very low power optical communications system for miniature robots, as small as 1 cu cm is addressed. The communication system is a variant of photon counting communications. Instead of counting individual photons the system only counts the arrival of time coincident sets of photons. Using sets of photons significantly decreases the bit error rate because they are highly identifiable in the presence of ambient light. An experiment demonstrating reliable communication over a distance of 70 meters using less than a billionth of a watt of radiated power is presented. The components used in this system were chosen so that they could in the future be integrated into a cubic centimeter device.
One concept for planetary exploration involves using many small robotic landers that can cover more ground than a single conventional lander. In addressing this vision, NASA has been challenged in the National Nanotechnology Initiative to research the development of miniature robots built from nano-sized components. These robots have very significant challenges, such as mobility and communication, given the small size and limited power generation capability. The research presented here has been focused on developing a communications system that has the potential for providing ultra-low power communications for robots such as these. In this paper an optical communications technique that is based on transmitting recognizable sets of photons is presented. Previously pairs of photons that have an entangled quantum state have been shown to be recognizable in ambient light. The main drawback to utilizing entangled photons is that they can only be generated through a very energy inefficient nonlinear process. In this paper a new technique that generates sets of photons from pulsed sources is described and an experimental system demonstrating this technique is presented. This technique of generating photon sets from pulsed sources has the distinct advantage in that it is much more flexible and energy efficient, and is well suited to take advantage of the very high energy efficiencies that are possible when using nano scale sources. For these reasons the communication system presented in this paper is well suited for use in very small, low power landers and rovers. In this paper a very low power optical communications system for miniature robots, as small as 1 cu cm is addressed. The communication system is a variant of photon counting communications. Instead of counting individual photons the system only counts the arrival of time coincident sets of photons. Using sets of photons significantly decreases the bit error rate because they are highly identifiable in the presence of ambient light. An experiment demonstrating reliable communication over a distance of 70 meters using less than a billionth of a watt of radiated power is presented. The components used in this system were chosen so that they could in the future be integrated into a cubic centimeter device.
One way to improve the acquisi tion of planetary information from robotic landers is to use many smaller robotic explorers that can cover more ground than a single conventional rover , given that the existing launch capabilities constrain the mass of planetary robotic landers to a relati vely fixed value . In addressing this vision, NASA has been challenged in the National Nanotechnology Initiative to research the development of miniature robots built from nano -sized components. These robots have very significant challenges, such as mobil ity and communication, given the small size and limited power generation capability. The research presented here has been focused on developing a communications system that has the potential for provid ing ultra -low power communications for robots such as t hese. In this paper an optical communications technique that is based on quantum entangled photons is presented. This technique both minimizes radiated power and is appropriate for the size scale of the robot. Simulations of this system show that the rad iated power may be reduced to extremely low levels for line -of -sight communication over distances of several kilometers, even in the presence of ambient light. The immunity to background noise makes this technique very promising in comparison to classical optical communications for ultra -low power applications. The results of t his research will generate requirements definitions for transceiver components built from nanotechnology. Results from experiments demonstrating aspects of this communications techn ique are presented.
In this paper a very low power optical communications system is addressed that could be developed specifically for creating networks involving a planetary lander and fixed or mobile sensor stations that could be as small as 1 cm3. The communication system is a variant of photon-counting based communications. Instead of counting individual photons, the system only counts the arrival of time coincident sets of photons. Using sets of photons significantly decreases the bit error rate because they are highly identifiable in the presence of ambient light.An experiment demonstrating reliable communication over a distance of 70 m using less than a billionth of a watt of radiated power is presented. The experiment also compares this technique to traditional photon counting and successfully demonstrates that time coincident photon communications can achieve an equivalent bit error rate at a signal-to-noise ratio that is 5 to 7 dB lower than what is needed for classical photon counting communication. The components used in this system were chosen so that they could in the future be integrated into a cubic centimeter device.
An important issue in today’s information society is the security of data transmission against potential intruders, which always put at risk the confidentiality. Current methods to increase security require that the two parties wishing to transmit information, exchange or share one or more security keys. Once the key has been identified, the information can be transferred in a provable secure way using a one-time pad, i. e. the key length is as long as the plaintext. Therefore, the security of the information transmission is based exclusively on the security of the key exchange. Quantum cryptography, or more precisely quantum key distribution (QKD), guarantees absolutely secure key distribution based on the principles of quantum physics, according to which it is not possible to measure or reproduce a state (e.g. polarization or phase of a photon) without being detected. The key is generated out from the measurement of the information encoded into specific quantum states of a photon, named qubits. For example, a qubit can be created using properties such as the polarization or the phase of a photon. Achieved goals of this thesis are the development of a new class of high speed integrated photonic sources for applications in quantum key distribution systems, capable of producing unprecedented qubit rates (100 Mbps - 1 Gbps) and transmitting those over larger distances than those achieved so far (> 200 km). More specifically the work has been focused on developing faint pulse sources which can be used in very demanding environmental conditions, such as those in Space. For the development of these sources, apart from the optical design, essential is the opto-mechanical engineering as well as the integration with the electronics. One of the objectives was to achieve very high level of integration and power efficiency, e.g. volumes and power consumption between 10 and 100 times smaller than those typical of a laboratory experiment. Moreover, work in related parts of a whole QKD transmission system has been carried out. In particular, a new scheme for a compact, fast and simple random number generator has been demonstrated successfully achieving a random number generation rate of 1:1 Gbps. Also, during the course of this thesis, the development and engineering of a free-space QKD optical link has been initiated. This thesis makes use of novel ideas to alternatively demonstrate proof-of- concept experiments, which could then further develop into commercial products. To this end, close collaborations with world-wide leading companies in the field have been established. The Optoelectronics Group at ICFO has been involved in current European Space Agency (ESA) projects to develop a small footprint and low power consumption quantum transceiver and a high-flux entangled photon source.
Abstract In this paper the procedure for automating the photon quantum experiments for mobile robotic applications is presented. Due to the rapid advances of quantum technologies and quantum engineering, the integration of quantum capabilities in robotic and autonomous systems will be inevitable, and therefore the study and investigation of compatibility and adaptability of quantum systems and classical autonomous systems is of great importance. In a quantum-classical hybrid setup, the source of single photon generation is placed on a leader robot which can send correlated single photons to robot followers. In the case of quantum entanglement, spontaneous parametric down-conversion process using nonlinear paired BBO crystals is implemented which sends entangled photons to the single photon counting modules installed on mobile robots. In the case of quantum cryptography, single photons are sent from Alice robot to Bob robot, where Alice has the course of single photon and Bob has a polarizing beamsplitter and two detectors and that can detect the polarization of photons as vertical and horizontal. Bob then can convert the polarizations to a digital signals as zeros and ones and use them as communication information for control purposes through a classical channel. Motorized optics equipment can automatically align the source of photons to detectors on the mobile robots. The automated alignment procedure is one of the key enabling technologies in integrating quantum capabilities with control of mobile robotic systems. In this paper, in particular, the automated alignment is studied while considering the uncertainties in the dynamic of the system which can potentially cause the alignment task very challenging. The uncertainty analysis in the automated alignment is implemented by Optimal Uncertainty Quantification technique to ensure achieving the quantum control of the robotic systems and presented here for the first time.
The signal intensity as a function of range is considered for optical communication systems that utilize time-coincident pairs (or larger sets) of photons for information encoding. Two systems are examined: one that generates pairs of photons that have an entangled quantum state, and another where the pairs of photons are generated from a pair of pulsed photon sources. The signal intensity as a function of range is analyzed as a qualitative first-order approximation for these two techniques. For the first time, to this author's knowledge, it is shown that pairs of photons that share a quantum state, and hence have highly correlated momenta, can produce communication systems that have a high degree of noise immunity and are useful for ranges significantly beyond the collimated range of the transmitter, which up until now has been considered the maximum range. As an example, it is shown that a transmitter with a 1-m aperture and a pair of pulsed photon sources will be effective for about 200 km, while a transmitter with the same aperture and a quantum-entangled photon source will have an effective range greater than 60,000 km.
Quantum communications and quantum cryptography are developing rapidly during the last decades caused partly by a fast progress in quantum computing. Quantum cryptography provides an unconditionally secure way of communicating whereas traditional classical cryptographic protocols are likely to be broken by super powerful quantum computers. In the past few years distances covered by quantum communications have increased by an order of magnitude. To provide a global coverage for the quantum networks, a satellite based quantum communications is the most promising solution. \n \nAs an emerging field, QKD systems are still under evolution process. Despite outstanding security proven theoretically, it has loopholes caused by their implementations. To test QKD, find the possible loopholes and suggest ways to fix them, is a job of many scientific groups. \nIn this thesis I start with presenting my work for a securing test of a commercial QKD system Clavis2. A Trojan-horse attack on Bob's apparatus was prepared by testing reflections and transmissions of all optical components in Bob's scheme. The attack was implemented and found to be unsuccessful at the tested wavelengths due to afterpulsing effect in Bob's single-photon detectors reacting to the bright light attack pulses. \n \nThree chapters of the thesis are dedicated to custom built single-photon detectors (SPDs) based on commercial Silicon avalanche photodiodes (APDs). Those detectors demonstrate parameters that altogether are not possible to find in commercially available SPDs, especially if combined with a very compact size. One of the in-lab-built SPDs was implemented in 143 km teleportation experiment, where a low dark count rate was crucial for the success of the experiment. The next generation SPD is already built, characterized and ready to be implemented. \n \nAnother 4-channel SPD was built as a prototype for a quantum satellite SPD. It has light weight, low electrical power consumption, low dark count rate and decent other parameters. It was used in the airborne demonstration of QKD receiver payload experiment, when a secret key was successfully generated between a moving aircraft and a ground station. \n \nSPDs installed on a satellite have to be able to work in the harsh space environment during a mission life time. Space radiation dramatically increases dark count rate of APDs. The last project presented in the thesis committed to a radiation test of three types of APDs and one type of photo multiplier tube. The experiment included characterization of all SPDs before and after irradiation by four levels of proton radiation, equivalent to 3 months - 2 years duration in a 600 km low Earth orbit. Three methods for mitigating radiation damage were tested and found to be successful with perspective to use some of them on a quantum satellite to extent life time of SPDs. \n \nTo summarize, this work makes a contribution to the development of SPDs for global quantum communications.