Quantum Technology for Aerospace Applications

Transcription

1 Quantum Technology for Aerospace Applications Bin Jia a, Khanh Pham b, Genshe Chen 1a, Dan Shen a, Zhonghai Wang a, Gang Wang a, Erik Blasch c a Intelligent Fusion Technology Inc. Germantown, MD b Air Force Research Lab, Kirtland AFB, NM c Air Force Research Laboratory, Rome, NY ABSTRACT In this paper, quantum technology is introduced with three key topics, including quantum computing, quantum communication, and quantum devices. Using these dimensions of quantum techniques we briefly introduce their contributions to aerospace applications. The paper will help readers to understand the basic concepts of the quantum technology and their potential applications in space, air, and ground applications such as highly accurate target positioning. Keywords: Quantum technology, Quantum computing, Quantum communication, Quantum devices. 1. INTRODUCTION Quantum technology is an emerging concept based on quantum physics. Quantum techniques have attracted the attention of many researchers and organizations around the world. For example, the United Kingdom funded 270 million pounds to covert quantum-physics research into commercial products [1]. In addition, Google, NASA, and the nonprofit universities Space Research Association have joined to install a D-Wave Two [2], a commercial quantum computer based on the quantum technology. One interesting question is how quantum technology can be used in aerospace applications. In fact, quantum technology is very suitable to be applied in space missions because space provides an ideal environment for quantum technology. Specifically, long interaction time can be obtained due to the microgravity [3]. In addition, the space environment provides a quiet situation for testing quantum related techniques [3]. Although it is still an open question on how to use quantum technology for real space applications, it can potentially change the world of aerospace operations. Hence, in this paper, we briefly review typical space applications that could benefit from quantum technology. In this paper, we arrange the discussion be identifying three areas of quantum technology: computing, communication, and devices. The rest of this paper is organized as follows. Section 2 introduces some basic and relevant concepts of quantum mechanics. In Section 3, techniques used for quantum computing as well as potential space applications are introduced. In Section 4, the techniques used for quantum communication are described with an example of aerospace mission. Section 5 discusses quantum devices for space application. Concluding remarks are given in Section QUANTUM MECHANICS BASIC Instead of introducing too much about the quantum mechanics, five important elements of quantum mechanics related to this paper are concisely introduced in Section Superposition state The quantum bit, denoted by, has infinite choices of so-called superposition states. Using mathematics, is spanned by a basis consisting of two basic states, 0 and 1 [4], i.e., 0 1 (1) 1 gchen@intfusiontech.com; phone ; fax Sensors and Systems for Space Applications VII, edited by Khanh D. Pham, Joseph L. Cox, Proc. of SPIE Vol. 9085, 90850S 2014 SPIE CCC code: X/14/$18 doi: / Proc. of SPIE Vol S-1

2 where and are two coefficients. From Eq. (1), it can be seen that can represent any state of the quantum bit by choosing different and. The superposition state is very useful for parallel computing, of which more explanation will be given in Section Entanglement Quantum entanglement is a physical phenomenon that particles are interacted or generated in a way that the quantum state cannot be described independently [5]. Two quantum bits have four basic states, say: 0 0, 0 1, 1 0, and 1 1, where the subscript i for i=1,2 denotes the ith quantum bit. When considering the superposition state of two states, we have, (2) It is clear that the state cannot be rewritten in factored form of two quantum bits. Hence, these two quantum bits 12 are dependent on each other. Entanglement is very useful in quantum communication, which will be introduced in Section Interference Quantum particles can cross their own trajectory and interfere with the direction of their paths. Based on Thomas Yong s experiments, interference takes place between the waves/particles going through the slits [6]. For quantum particles, they are interfering with themselves. Feynman pointed out that each photon simultaneously traverses every possible trajectory en route to the target [6]. This property can be used for quantum computing and cryptosystem. Based on the interferer, parallel speedup for a quantum computer can be realized [7]. 2.4 Measurement Quantum systems are fragile in terms of measurement. Measuring the state of a quantum bit will yield 0 or 1. In general, the state of the quantum bit described by Eq. (1) is random and with probabilities 2 and 2 to be 0 and 1, respectively [4]. Measuring the state of the quantum bit changed the state to 0 and 1 irreversibly. Hence, measuring of the quantum system is fragile but it can be used for cryptosystem. 2.5 No cloning Without touching the original quantum system, it is physically impossible to copy the state of it to another one [4]. However, creating a copy of the quantum bit will destroy its state. This property is important for quantum cryptosystem. 3. QUANTUM COMPUTING The conventional computer uses bit (0 or 1) to represent the data. The quantum computer operates on so-called qubits, which are the quantum analog of classical bits. Quantum computation relies on quantum mechanics, which describes the behavior and properties of the elementary particles [8]. The current 35nm circuit technology approaches the limit since the dimension is considered close to the size of an atom. To overcome the limit of conventional circuit design technology and mitigate the increasing demand of the computational power, the exploration of the quantum mechanics and quantum computing becomes important. However, quantum computing is fundamentally different to what we use in an existing computer. First, in conventional computers, a bit is used to represent the information which can be 0 or 1. The bit represents the state of a transistor or the presence/absence of charge in the memory cell. In quantum computers, a quantum bit, also called qubit is used. Besides 0 and 1, the qubit can take on the properties of 0 and 1 simultaneously at any time. The state is so-called superposition state which can be used to represent multiple information simultaneously. For multiple qubits, say N qubits, there are 2 N states can be represented simultaneously. The classical bit is compared to the quantum bit in Figure 1 [9]. Proc. of SPIE Vol S-2

3 As shown in Figure 1, either 0 or 1 is used for classical bit. Although N bits are used, only one out of 2 N can be represented. For the quantum bit, both information of 0 and 1 can be represented simultaneously. Hence, it can be inferred that qubits are very useful for computation when lots of permutations are required. To the best of the authors knowledge, the only commercial quantum computer is created by the D-Wave Systems Inc. As an example, D-Wave 2 quantum computer is shown in Fig. 2. Currently, it operates in an extreme environment and enables the quantum algorithms to solve very hard problems. More details about the hardware can be found in [10]. It is should be emphasized here quantum algorithms need be developed to use such a computer. Quantum computing can be used in many space missions. For example, for space exploration verification, critical modeling and simulation of aerodynamic performance is required to understand different pehnomenon. Due to the highly promising computational power, the NASA quantum artificial intelligence laboratory (QuAil) houses a 512-qubit D- Wave Two TM quantum commuter. NASA wants to use the D-Wave Two for the following two missions. The first is the NASA Kepler mission, which aims to search for habitable, Earth-size planets [11]. To identify and validate the transit signals of small planets as they orbit their host stars, the heuristic algorithms are used to process large quantities of data. Some planets may be undiscovered due to the computational limitation of conventional super computers [11]. The Quantum computer; however, performs data-intensive search for transiting planets which is potentially a unique, complementary approach for this task. The second is for planning and scheduling tasks which commonly exist in space missions, such as determining the observation time of a target using radar. Automated planners are extensively used in space missions. However, it has required hours, days, or even weeks to get the solution. The quantum computer can greatly reduce the time of the computation to improve the efficiency [11]. 3 t en Classical Bit N 8R,,,á.; -x--._ Either 0 or 1 One out of 2" possible permutations 1 Bn Quantum Bit NEIN e < `11, '.40 A -d Both 0 and 1 All of 2" possible permutations Figure 1: Comparison of Classical Bit and Quantum Bit [9] Exterior of D-Wave 2 Interior of D-Ware 2 Figure 2: D-Wave 2 Quantum Computer [10] 4. QUANTUM COMMUNICATION The basis of the quantum communications is entanglement. For the entangled particles, if the spin of one of the particles changed, the spin of this entangled counterpart will nearly be instantaneously changed, even if they are miles away. Due to the interference of the weather, the maximum distance of the quantum communications is about 90 miles. For a space environment, due to the less chance of atmospheric interference, provides an ideal situation for quantum communications. Hence, space-based quantum communication becomes an increasingly popular use of quantum computers. Researchers are interested in quantum communication, although it is fragile. The reason is that the quantum communication is almost perfectly secure. In general, the communication message is encrypted by the key which is transmitted by the entangled photons. Hence, the change of the key can be almost be instantly known by the sender. Theoretically, a quantum encrypted network is almost perfectly secure which revolutionizes communication performance. For now, it is rare to use the quantum communication to transfer data. Instead, it is commonly recommended to distribute secret keys, as the so-called, quantum key distribution (QKD). QKD is a promising technique for the space applications [12]. For satellite-to-ground quantum communication, transmission losses are mainly due to the atmosphere. In addition, the sender location on the satellite and receiver position on the ground can be changed with respect to each other. The polarization of entangled particles rotates relative to each other all the time. Hence, compensation algorithms Proc. of SPIE Vol S-3

4 are proposed [13, 14]. As summarized in [14], future free-space QKD schemes can be applied in two schemes [14]. As shown in Figure 3, the first scheme is based on the faint pulse quantum communication. Symmetric key encoding is used in the space satellite modules and the decoding is implemented on the ground. The quantum key is uploaded to satellites and the key is used for securing the data. The data are then transmitted by the satellite to the licensed users only. The second scheme, as shown in Figure 4, uses entangled photons. Two optical paths from the space satellite communication module to the ground communication module are required. The disadvantage is that the error rate is increasing. In addition, for two users, Alice and, can move with respect to each other with the rotation of the Earth. Hence, the compensation algorithm of this movement in polarization based satellite-to-ground QKD is required to maintain communication. Currently, it is difficult to control and use entangled particles in practical implementations. Alice Alice satellite LEO satellite.i,._ i,, // \\ entanglement Alice LEO satellite entanglement I Ground Figure 3: The first scheme [14] Figure 4: The second scheme [14] There are also many proposed solutions for practical space quantum communications. For example, the International Space Station (ISS) is proposed to act as a quantum communication relay [15]. The optical ground station is used as a transmitter to send one photon of an entangled pair to ISS. The dedicated photon detection module is required to replace the camera presently in use. Theoretically, the entanglement is independent of distance. A series of tests are proposed to determine the effect of distance and the interplay between gravitation and entanglement performance of quantum communication [15-17]. If the proposed method works, the international space station can act as a relay to send quantum encryption keys in the satellite communication networks [15]. Although the proposed solution is promising, more developments are required, such as the investigation and compensation for the effects of gravity. In [16], researchers found that the gravity affects the propagation of photons, which means additional noise is added to the channel for transmission of information. As another topic [17], entangled particles in two separate satellites which are in the same orbit could be transferred. One of the satellites is then maneuvered to a different orbit. The entanglement is degraded after the maneuver. It is shown that entanglement oscillates periodically with the difference in gravitational potential of the orbits. Therefore, the satellite position has to be precisely controlled to conserve entanglement. To the best of the authors knowledge, there is no quantum satellite currently in use. Much work is required to use space communication to transfer data. However, many countries, including Canada, China, and Japan are working to put experimental quantum key distribution (QKD) satellites into space [18]. Ground 5. QUANTUM DEVICES FOR AEROSPACE MISSIONS By using quantum technology, many practical sensors will be produced. There are some important sensors essential for aerospace applications. In this section, two important sensors as well as their applications are introduced such as inertial sensors and optical clocks. It has been pointed out that the interactions between atoms and a laser light resulted in the atom interferometers, which has been used in the development of practical atomic quantum inertial sensors [19]. In fact, the particle-wave duality of atoms can be used to obtain ultra-sensitive interferometry measurements. Wave properties of atoms, however, are difficult to control. Fortunately, the advent of laser-cooling techniques reduces the motional temperature of atoms so that atom optics can be implemented. There are many unique characteristics of the atomic interferometer. For example, the matter-wave interference can be used for displacement measurements. In addition, this technique is suitable for space applications because the microgravity environment offers long interrogation time with atoms which will eventually result in orders of magnitude higher sensitivity compared with terrestrial measurements [19]. It has been indicated that laboratory atom interferometer already surpasses the state-of-the-art traditional sensors [19]. The atomic quantum ' Proc. of SPIE Vol S-4

5 inertial sensor is very useful for developing new generation guidance, navigation, and control (GNC) space satellite systems. Many new sensors, such as an accelerator, gyroscope, and magnetometer can be produced using quantum technology for space missions [20, 21]. As shown in Figure 5, for a general control system, the assessment of the object requires accurate measurement. To precisely control the satellite, accurate measurement is desired. Due to the high accuracy of the measurement, the precise position or attitude of satellite can be obtained. In addition, many important physics experiments can be done based on the atom interferometers, such as detection of the gravitational-wave. Sensing (Clock, Inertial Sensor, Image Sensor,...) Computation Control/Actuation Figure 5: Illustration of the control system The second sensor very useful for the space application is the high accuracy optical clocks. Atoms can be well controlled using the laser cooling and trapping of ions. This new type of clock is based on the optical atomic transitions which dramatically improves timing over conventional microwave transitions. The optical clock operates with a much smaller unit of time that the microwave clock. Hence, the highly accurate clock can be designed. The performance of microwave 13 clock is limited to level while the optical clock can routinely achieve 10 level [19], which is much more accurate than the microwave clock. A highly accurate clock is essentially important for many space missions such as the global positioning system (GPS). The GPS receiver computes the distance to the satellite using the speed of the light and the transit time. Hence, the preciseness of time determines how accurate the localization is. As shown in Figure 6 [22], for an ideal case, both the satellite and the receiver have a perfect clock under the assumption that the signal is not affected by noise. In this case, three intersection spheres can determine the location of the receiver uniquely. Unfortunately, the signal is commonly corrupted with noise. Hence, an additional satellite is required to determine the time offset of the GPS receiver clock. Thus, in the future, with the help of the high accuracy clock, the accuracy of the satellite position can definitely be improved. Besides GPS, space provides an ideal environment to test the laws of physics related to time metrology. GPS solution (Ideal Case), intersection of 3spheres -} GPS solution (2D case). Area created in a Non Ideal Case. An additional satellite is required for solution. Figure 6: Localization using GPS [17] Proc. of SPIE Vol S-5

6 Other quantum sensors are also very potential for the space applications, for example, quantum illumination, which is to determine the presence or absence of weakly-reflecting target [19]. Researchers have shown that quantum illumination significantly outperforms conventional remote sensing instruments when the region of interest has high-brightness and the signature of interest is weak. The application of remote sensing is critical for many global applications, such as climate change. The quantum illumination sensor can also be extended to provide secure communications. 6. CONCLUSION Quantum technology will fundamentally change the world and it has potential in many space applications. Space applications include the Global positioning system, Guidance, Navigation, and remote sensing. More applications based on quantum technology, such as quantum computing, quantum communication, and quantum devices can be foreseen in the near future. The research of the quantum technology requires cross-interdisciplinary studies to realize the power of quantum technology over conventional systems. REFERENCES [1] [2] [3] Bresson, A., Bidel, Y., Bouyer, P., Leone, B., Murphy, E., and Silvestrin, P., Quantum mechanics for space applications, Applied Physics B, 84 (4), (2006) [4] Spiller, T. P. Basic elements of quantum information technology. Introduction to Quantum Computation and Information, (1997) [5] [6] [7] Shiekh, A. Y., The role of quantum interference in quantum computing. International Journal of Theoretical Physics, 45(9), (2006). [8] roduction_and_quantum_mechanics.pdf [9] [10] [11] [12] Wang, P., Zhang, X., Chen, G., Pham, K., and Blasch, E., Quantum key distribution for security guarantees over QoS-driven 3D satellite networks, Proceedings of SPIE, 9085, (2014). [13] Wang, G., Shen, D., Chen, G., Pham, K., and Blasch, E., Polarization tracking for quantum satellite communications, Proceedings of SPIE, 9085, (2014). [14] Bacsardi, L., and Imre, S. Quantum Based Information Transfer in Satellite Communication, Satellite Communications, Sciyo, (2010). [15] Scheidl, T., Wille, E., and Ursin, R. Quantum optics experiments using the International Space Station: a proposal, New Journal of Physics, 15 (4), (2013). [16] Bruschi, D. E., Ralph, T., Fuentes, I., Jennewein, T., and Razavi, M. S, Spacetime effects on satellite-based quantum communications, arxiv preprint arxiv: (2013). [17] Bruschi, D. E., Sabín, C., White, A., Baccetti, V., Oi, D. K., and Fuentes, I. Testing the effects of gravity and motion on quantum entanglement in space-based experiments, arxiv preprint arxiv: (2013) [18] [19] Erkmen, B. I., Shapiro, J. H., and Schwab, K. Quantum Communication, Sensing and Measurement in Space, Keck Institute for space studies, (2012). [20] Jia, B., Xin. M., and Cheng, Y., Sparse Gauss-Hermite quadrature filter for spacecraft attitude estimation, Proceedings of American Control Conference, , (2010). [21] Jia, B., Xin, M., and Cheng, Y. Vision-based spacecraft relative navigation using the sparse Gauss-Hermite quadrature filter, Proceedings of American Control Conference, , (2012). [22] Nemra, A. and Aouf, N. Robust INS/GPS sensor fusion for UAV localization using SDRE nonlinear filtering. Sensors Journal, IEEE, 10 (4), (2010). Proc. of SPIE Vol S-6