As secure space communications becomes more desirable, quantum based communications systems have the potential to become a high performing option. NASA/GSFC with its partner institutions is pursuing a variety of technology thrusts to enable the practical application of quantum communications in future NASA missions. This paper will discuss some of those technology areas. We will discuss methods being developed by GSFC and University of Kansas for securing and auto-synchronizing communication over free-space optics using quantum key distribution and chaotic systems. In such a scenario, the security of the system would stem from the sensitivity to initial conditions. Furthermore, specific windows of single chaotic runs can be harvested to be used with encoder/decoder in a cyclic manner. Not only would the security of such a system be unique, the initial conditions can be transmitted via a quantum key distribution to add another layer of security to the system. We will discuss work being performed by GSFC and Michigan State University in analysis and development of solid-state quantum communications materials and devices. These will be necessary for devices capable of processing and routing quantum information on-board a spacecraft or within a quantum-capable ground station. In recent years, advancements in the understanding of quantum properties has led to a wide range of promising applications. One such application is orbital angular momentum (OAM) for secure optical communications being researched by partners at University of Wyoming and University of Illinois-Chicago The utilization of OAM properties can be done via highly precise function values that can then be modulated using different constellations. Opportunities for quantum communications demonstrations exists in a variety of possible venues from balloons to CubeSats. We will discuss the potential for a low cost, high altitude balloon-to-balloon quantum communications demonstration to be carried out under the University of Wyoming Space Grant.
There has been an explosion of research in the area of quantum computing and quantum communications. There is the groundbreaking work by Paul Kwiat, et. al. in the Quantum Information Group at the University of Illinois, some of which as sponsored by NASA with collaborators at JPL  ,  ,  . There is also the highly significant research, broad-based research in the characteristics of quantum space links conducted in Austria at the Institute for Quantum Optics and Quantum Information  . Within NASA, GSFC and its partners are also engaged in research involving quantum phenomena including quantum sensors, quantum computing, and quantum communications. In this paper, we describe some of the activities related to quantum communications that are under investigation within the Exploration and Space Communications (ESC) division of GSFC. We are a group of part-time researchers developing technology for future US laboratory experiments in quantum communications and computing while training students in these technologies. We include university partners and GSFC civil servant and contractors.
The main purpose of this paper is to acquaint a broad audience of some of the activities under way at GSFC and capabilities that are available to advance quantum communications technologies.
We have a deep background in nanomaterials, simulation and modelling of quantum materials, information theory, quantum mechanics, and novel forms of communications. All of our activities include student involvement through the use of strategic student internships. Each of the external collaborator institutions supplies undergraduate and graduate students to work alongside professionals at GSFC. The students get involved in mission planning and design, systems engineering, and technology development. The students are directly supervised by former interns who have become NASA employees. The former interns develop their project management and technology development skills. Current interns can see a path to future NASA employment, and we maintain a pipeline of excellent students that will replenish the NASA workforce as it ages. Given a generic block diagram for a quantum communications architecture as shown in Fig.1 , all of the activities being undertaken fit somewhere in one or more blocks of the architecture. Fig. 1 . Generic architecture for a quantum communications system. It applies to both space and ground applications
The professionals on the GSFC team have been involved in a variety of classical optical communications projects including the Lunar Laser Communications Demonstration  in 2013 and the upcoming Laser Communications Relay Demonstration  to be launched in 2020. We leverage that experience in the development of quantum communications for space.
The main goals of this research program are: Provide an educational experience for US undergraduate and graduate students in quantum theory and phenomena through real-life projects to develop quantum entangled communications systems for flight Develop a low-cost approach to the development of quantum entangled communications systems that can evolve into fully functional quantum entangled communications systems for NASA Develop a self-supporting network of collaborators pursuing various aspects of quantum communications Support the US National Quantum Initiative
2. Synergy With The Classical Optical Communications Projects
The development of a quantum optical communications at GSFC requires taking a path that leverages the classical optical communications work. This path can leverage on developments in classical laser communications. Advances in classical coding theory using LDPC could continue to be implemented in a quantum communications scheme as well as classical optical communication modulation techniques such as mary Pulse Position Modulation (PPM), Differential Quadrature Phase Shift Keying (DQPSK) and others. Our plan is to leverage technology from the LCRD mission into quantum entanglement deployment efforts.
3. Student Intern Project -Quantum Entangled Stratospheric Telecommunications (Quest)
A team of students from the collaborator institutions came to GSFC in the summer 2019 to begin development of a student project to implement quantum-entangled communications. The activity involves a partnership with the University of Wyoming High Altitude Balloon research conducted under their National Science Foundation Grant. The goal is a balloon-to-balloon demonstration. Students were assigned to develop all parts of the mission. The important point that was stressed by NASA was the large amount of work required to develop a workable mission around the quantum entanglement experiment. Thus, the graduate physics major was assigned to the science team and the engineering majors were tasked to work interactively with the science team to achieve the mission objectives. This is how NASA projects typically work: Engineers come up with solutions to achieve science objectives.
It was also decided that the student team would work from a defined set of requirements. This would focus the team on developing an implementation approach around requirements.
3.1 Mission Requirements And Student Implementation Path
|1||Demonstrate secure quantum entangled|
|communications between source and destination points|
|2||At least one of the two points must include a payload on a flying balloon as part of the demonstration.|
|3||The team shall determine the distance between source and destination as part of their design.|
|4||Quantum entanglement has to be demonstrated at 600-770 nm wavelength|
|5||Implement a quantum security protocol as part of the demonstration.|
|6||The team shall develop a block diagram of the demonstration with all the pieces and their links and interconnections with a description, and a description of the concept of operations for the mission.|
|7||The communications payload has to be retrievable and reusable.|
The intern team was given a set of Level 1 requirements as guidance in developing the project. The Level 1 requirements were decomposed into Level 2 requirements by the Systems Engineer. The Level 1 requirements are shown in Table 1 . At least one of the two points must include a payload on a flying balloon as part of the demonstration. 3
The team shall determine the distance between source and destination as part of their design. 4 Quantum entanglement has to be demonstrated at 600-770 nm wavelength 5 Implement a quantum security protocol as part of the demonstration. 6
The team shall develop a block diagram of the demonstration with all the pieces and their links and interconnections with a description, and a description of the concept of operations for the mission. 7
The communications payload has to be retrievable and reusable.
As a minimum, the payload must include a quantum entangled modulator and transmitter for the transmit function and a quantum entangled demodulator and receiver for the receive function. The functions can be separate enclosures if necessary. 9
There shall be a data source that produces classical data to feed the transmit function and a method to determine bit error rate of the demonstration 10 The PI and the team shall document the criteria for proving that successful entanglement has occurred over the link between source and destination. 11 There shall be an atmospheric monitoring system for the visible to Near IR wavelengths that can provide cloud free line of sight data to the mission 12 Develop an integrated schedule and a rough order of magnitude cost estimate for the entire mission.
The interns decided upon a two-balloon mission concept as shown in Fig. 2 . The mission concept is still undergoing analysis against potential alternatives e.g. ground-to-balloon quantum entanglement. The implementation trades over the space of payload mass, buoyancy, altitude, mission lifetime and payload recovery without damage were performed by the University of Wyoming students. Fig. 2 . The student high-level concept for a two-balloon experiment that would involve one way communications from a transmitter balloon to a receiver balloon with fully autonomous operations at an experiment altitude from 15km to 20km with no ground communications. Experiment results to be retrieved upon retrieval of the payloads.
3.2 Summary Of Quantum Entanglement Experiment
The University of Wyoming developed the concept for quantum entanglement experiment as summarized in Fig. 3 . The underlying protocol is being simulated and refined as part of his dissertation work.