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之前大家对揽瓜阁精读的反馈很好，就想着自己的时间开始把一些精读的文章根据JJ出题目～ 然后focus上线，IR需求 大家也大。就想着 把揽瓜阁的阅读 逻辑 IR 都放在这贴里打卡
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1.CR
In a distant galaxy, the rate of star formation has been decreasing. Typically, a decrease in star formation leads to a reduction in cosmic radiation as fewer massive stars explode as supernovae. However, despite the declining rate of star formation, astronomers have observed an increase in the intensity of cosmic rays, citing the presence of highly energetic particles. Which of the following, if true, best explains the apparent contradiction?
(A) The galaxy has a supermassive black hole at its center that is actively consuming matter and emitting intense radiation.
(B) The decrease in star formation has led to a reduction in the amount of interstellar dust, allowing cosmic rays to propagate more easily.
(C) The galaxy has experienced a recent merger with another galaxy, triggering a temporary increase in star formation and cosmic radiation.
(D) The astronomers' instruments have become more sensitive, allowing them to detect cosmic rays that were previously unnoticed.
(E) The galaxy has a large number of old, low-mass stars that emit minimal cosmic radiation.
Scientists have observed that in a certain galaxy, a large number of stars exist in binary systems where two stars orbit each other. However, recent findings show that among the 2,000 planetary systems discovered in this galaxy so far, only 50 are binary systems, while the vast majority consists of single planets.
Which of the following, if true, would most undermine the scientists' findings?
(A) The scientists are unable to determine conclusively whether a given planetary system is binary or not based on current observation methods.
(B) The single planets observed are still in the process of forming their companion planets, which takes a long time.
(C) Binary planetary systems are much harder to detect than single planet systems with current technology.
(D) In other galaxies, binary planetary systems are observed to be much more common than single planet systems.
(E) The 2,000 planetary systems observed so far only represent a tiny fraction of all planetary systems in the galaxy.
答案:
AC
The advent of quantum computing has heralded a paradigm shift in the field of cryptography, promising to revolutionize the way we secure sensitive information in the digital age. At the heart of this transformation lies the concept of quantum key distribution (QKD), a novel cryptographic protocol that leverages the fundamental principles of quantum mechanics to enable the secure exchange of cryptographic keys between two parties. Unlike traditional cryptographic methods, which rely on the assumed computational complexity of certain mathematical problems, QKD offers unconditional security guaranteed by the laws of physics.
The core principle underlying QKD is the quantum no-cloning theorem, which states that it is impossible to create an identical copy of an unknown quantum state. This property ensures that any attempt by an eavesdropper to intercept and measure the quantum states used in the key exchange process will inevitably introduce detectable errors, alerting the communicating parties to the presence of an intruder. By carefully analyzing the error rates in the exchanged quantum states, the parties can determine whether the key exchange process has been compromised and, if necessary, abort the communication and discard the compromised key.
One of the most promising implementations of QKD is the BB84 protocol, named after its inventors, Charles Bennett and Gilles Brassard, who first proposed the scheme in 1984. The BB84 protocol involves the use of polarized photons to encode the binary digits of the cryptographic key. The sender, typically referred to as Alice, randomly chooses one of four possible polarization states for each photon: horizontal, vertical, diagonal, or anti-diagonal. These states are grouped into two conjugate bases, known as the rectilinear and diagonal bases, which are mutually unbiased, meaning that measuring a photon in one basis provides no information about its state in the other basis.
Alice then transmits the polarized photons to the receiver, called Bob, who independently chooses to measure each photon in either the rectilinear or diagonal basis, recording the results of his measurements. After the transmission is complete, Alice and Bob publicly compare a subset of their measurement bases, discarding any photons for which their bases did not match. The remaining photons, for which their bases coincided, are used to generate the shared secret key.
The security of the BB84 protocol arises from the fact that any attempt by an eavesdropper, referred to as Eve, to intercept and measure the polarized photons will inevitably disturb their quantum states, introducing detectable errors. If Eve tries to measure a photon in the incorrect basis, she will obtain a random result, altering the photon's state in the process. When Alice and Bob compare their measurement bases, they will discover discrepancies in the results, indicating the presence of an eavesdropper.
To quantify the level of security provided by QKD, researchers have developed a framework known as the universal composable security model. This model considers the most general type of attack that an eavesdropper could employ, including the possibility of attacking the devices used in the QKD protocol. The security of a QKD protocol is characterized by its secret key rate, which represents the fraction of the raw key that can be used to generate a secure secret key, taking into account the information that may have been leaked to an eavesdropper.
Recent advancements in QKD technology have enabled the implementation of these protocols over increasingly longer distances. In 2018, a team of researchers from the University of Science and Technology of China (USTC) successfully demonstrated QKD over a record-breaking distance of 1,120 kilometers, using a satellite-based platform. This achievement marked a significant milestone in the development of global-scale quantum communication networks, paving the way for secure communication channels that transcend the limitations of terrestrial infrastructure.
Despite these impressive achievements, there are still significant challenges that must be overcome to realize the full potential of QKD in real-world applications. One of the primary challenges is the development of efficient and reliable single-photon sources and detectors, which are essential components of QKD systems. Current technologies, such as attenuated lasers and avalanche photodiodes, suffer from limitations in terms of efficiency, noise, and scalability, hindering the widespread adoption of QKD in practical communication networks.
Another critical challenge is the cost and complexity of QKD systems. Existing QKD devices often require sophisticated optical components, intricate control electronics, and dedicated cooling systems, resulting in high manufacturing and maintenance costs. To drive the widespread adoption of QKD technology, researchers are working on developing more compact and cost-effective QKD systems, leveraging emerging technology platforms such as integrated photonics and silicon photonics.
In addition to the hardware challenges, the practical implementation of QKD also requires addressing a range of network architecture and protocol design issues. To achieve end-to-end secure key distribution in complex communication networks, QKD protocols need to be seamlessly integrated with existing network infrastructure and security protocols. This necessitates the development of new network architectures and standards to support the deployment and interoperability of QKD systems.
The rapid advancement of quantum computing also poses potential challenges to the long-term security of QKD. Although QKD protocols offer unconditional security in theory, they are still vulnerable to attacks by quantum computers. In particular, the emergence of Shor's algorithm has demonstrated that quantum computers can efficiently solve certain types of mathematical problems, such as integer factorization and discrete logarithms, which form the basis of many classical cryptographic schemes. To address this threat, researchers are developing post-quantum cryptographic schemes that rely on mathematical problems believed to be difficult for both classical and quantum computers to solve.
Despite these challenges, QKD technology shows great promise in protecting critical communication infrastructures and sensitive data. As research continues to progress and technological advancements are made, the widespread deployment of QKD on a global scale is expected to become a reality in the near future. This development will mark a significant milestone in the field of cryptography, ushering in a new era of information security in the digital age.
1. What is the fundamental principle of quantum mechanics that underlies the security of quantum key distribution (QKD) protocols?
(A) Quantum entanglement
(B) Heisenberg's uncertainty principle
(C) Quantum no-cloning theorem
(D) Quantum teleportation
(E) Quantum superposition
2. In the BB84 protocol, how many mutually unbiased bases are used to encode and measure the polarized photons?
(A) 1
(B) 2
(C) 3
(D) 4
(E) 5
3. What is the primary consequence of an eavesdropper's attempt to intercept and measure the polarized photons in the BB84 protocol?
(A) The eavesdropper will be able to perfectly clone the photon's quantum state
(B) The eavesdropper's measurement will introduce detectable errors in the quantum states
(C) The eavesdropper will be able to determine the shared secret key without being detected
(D) The eavesdropper's presence will completely block the transmission of photons between Alice and Bob
(E) The eavesdropper will be able to manipulate the polarization states of the photons without being detected
4. Which of the following best describes the universal composable security model in the context of QKD?
(A) A model that assumes the eavesdropper has limited computational resources
(B) A model that considers the most general type of attack an eavesdropper could employ
(C) A model that focuses solely on the security of the quantum channel
(D) A model that ignores the possibility of device-level attacks
(E) A model that guarantees unconditional security against all types of attacks
5. What is the significance of the secret key rate in a QKD protocol?
(A) It represents the maximum distance over which the protocol can be implemented
(B) It determines the speed at which the shared secret key can be generated
(C) It quantifies the amount of information that can be transmitted per photon
(D) It represents the fraction of the raw key that can be used to generate a secure secret key
(E) It measures the level of entanglement between the polarized photons
6. What was the major milestone achieved by researchers from the University of Science and Technology of China (USTC) in 2018?
(A) Demonstrating QKD over a distance of 1,120 kilometers using a satellite-based platform
(B) Developing the first practical single-photon source for QKD systems
(C) Implementing a QKD protocol that is immune to attacks by quantum computers
(D) Achieving a secret key rate of 100% in a real-world QKD system
(E) Integrating QKD seamlessly with existing classical communication networks
7. What is one of the main challenges hindering the widespread adoption of QKD in practical communication networks?
(A) The lack of standardization in QKD protocols and network architectures
(B) The limited availability of high-quality optical fibers for long-distance QKD
(C) The inefficiency and noise limitations of current single-photon sources and detectors
(D) The incompatibility of QKD with existing classical encryption algorithms
(E) The inability of QKD to provide authentication of the communicating parties
8. How are researchers addressing the cost and complexity challenges associated with current QKD systems?
(A) By focusing on the development of purely software-based QKD solutions
(B) By leveraging emerging technology platforms such as integrated photonics and silicon photonics
(C) By abandoning the use of single-photon sources in favor of classical light sources
(D) By relying solely on satellite-based QKD systems to minimize infrastructure costs
(E) By compromising on the security of QKD protocols to reduce system complexity
9. What potential threat does the advancement of quantum computing pose to the long-term security of QKD?
(A) Quantum computers could be used to intercept and clone the polarized photons in QKD protocols
(B) Quantum computers might enable the development of new types of attacks that can bypass QKD security
(C) Quantum algorithms, such as Shor's algorithm, could efficiently solve mathematical problems that underpin classical cryptographic schemes
(D) Quantum computers could be used to manipulate the quantum states of photons in real-time, compromising the security of QKD
(E) Quantum computing could render the quantum no-cloning theorem obsolete, undermining the fundamental security of QKD
10. What is the significance of the development of post-quantum cryptographic schemes in relation to QKD?
(A) Post-quantum cryptography aims to replace QKD as the primary method for secure communication in the future
(B) Post-quantum cryptographic schemes are designed to be vulnerable to attacks by both classical and quantum computers
(C) Post-quantum cryptography is a complementary technology that can be used in conjunction with QKD to enhance overall security
(D) Post-quantum cryptographic schemes rely on mathematical problems that are believed to be difficult for both classical and quantum computers to solve
(E) Post-quantum cryptography eliminates the need for the development and implementation of QKD systems
CBBBDACBCD
Astronomers have always suspected that planets might orbit stars other than our sun. We imagined, though, that we would find systems much like our own solar system, centered on a star much like the sun. Yet when a flood of discoveries began 15 years ago, it was apparent right away that extrasolar planetary systems can differ dramatically from our solar system. The first example was the sunlike star 51 Pegasi, found to have a planet more massive than Jupiter on an orbit smaller than that of Mercury. As instruments became more sensitive, they found ever stranger instances. The sunlike star HD 40307 hosts three planets with masses between four and 10 Earth masses, all on orbits less than half the size of Mercury’s. The sunlike star 55 Cancri A has no fewer than five planets, with masses ranging from 10 and 1,000 Earth masses and orbital radii ranging from one tenth that of Mercury to about that of Jupiter. Planetary systems imagined in science fiction scarcely compare.
The white dwarf systems demonstrate that the stars do not even need to be sunlike. Planets and planetary building blocks can orbit bodies that are themselves no larger than planets. The variety of these systems equals that of systems around ordinary stars. Astronomers hardly expected the ubiquity of planetary systems, their hardiness and the apparent universality of the processes by which they form. Solar systems like our own might not be the most common sites for planets, or even life, in the universe.
It is sometimes forgotten today, but the first confirmed discovery of any extrasolar planets was around a very unsunlike star: the neutron star PSR 1257+12, an even more extreme type of stellar corpse than a white dwarf. It packs a mass greater than the sun’s into the size of a small asteroid, some 20 kilometers across. The event that created this beast, the supernova explosion of a star 20 times the mass of the sun, was more violent than the demise of a sunlike star, and it is hard to imagine planets surviving it. Moreover, the star that exploded probably had a radius larger than 1 AU (astronomical unit, the Earth-sun distance), which is larger than the orbits of the planets we see today. For both reasons, those planets must have risen up out of the ashes of the explosion.
Although supernovae typically eject most of their debris into interstellar space, a small amount remains gravitationally bound and falls back to form a swirling disk around the stellar remnant. Disks are the birthing grounds of planets. Astronomers think our solar system took shape when an amorphous interstellar cloud of dust and gas collapsed under its own weight. The conservation of angular momentum, or spin, kept some of the material from simply falling all the way to the newborn sun; instead it settled into a pancake shape. Within this disk, dust and gas coagulated into planets [see “The Genesis of Planets,” by Douglas N. C. Lin; Scientific American, May 2008]. Much the same process could have occurred in the post-supernova fallback disk.
Astronomers discovered the system around PSR 1257+12 by detecting periodic deviations in the timing of the radio pulses it gives off; such deviations arise because the orbiting planets pull slightly on the star, periodically shifting its position and thus altering the distance the pulses must travel. Despite intensive searches of other stars’ pulses, observers know of no other comparable system. Another pulsar, PSR B1620–26, has at least one planet, but it orbits so far from the star that astronomers think it did not form in a fallback disk but rather was captured gravitationally from another star.
1. The author's attitude towards the discovery of extrasolar planetary systems can best be described as one of:
(A) Cautious optimism regarding the potential for finding life on these planets
(B) Disappointment that these systems do not more closely resemble our own solar system
(C) Surprise at the diversity and resilience of planetary systems in the universe
(D) Skepticism about the accuracy of the methods used to detect these planets
(E) Concern that the unusual characteristics of these systems may pose challenges for future research
2. Based on the information provided in the passage, which of the following can be inferred about the formation of planets around pulsars?
(A) It requires the presence of a massive companion star to stabilize the orbit of the planets
(B) It is dependent on the magnetic field strength of the pulsar, which helps to attract debris from the supernova
(C) It occurs through a process similar to planet formation around sunlike stars, but on a much shorter timescale
(D) It is hindered by the intense radiation emitted by the pulsar, which vaporizes most of the available material
(E) It takes place in the fallback disk of material that remains gravitationally bound to the stellar remnant after the supernova
3. The passage suggests that the discovery of planets orbiting white dwarfs and pulsars challenges which of the following assumptions?
(A) Planets are most likely to form around stars that are similar in mass and size to our sun
(B) The processes of planetary formation are relatively rare and require specific conditions to occur
(C) Stellar remnants are unlikely to host planetary systems due to their small size and extreme environments
(D) Planetary systems are not capable of surviving violent events such as supernova explosions
(E) The detection of extrasolar planets requires the use of highly sensitive instruments and techniques
4. The author's statement that "Solar systems like our own might not be the most common sites for planets, or even life, in the universe" serves to:
(A) Highlight the unique characteristics of our solar system that make it particularly well-suited for life
(B) Suggest that the conditions necessary for life may be more prevalent than previously thought
(C) Imply that extrasolar planetary systems are unlikely to host life due to their unusual properties
(D) Encourage a reevaluation of the assumptions underlying the search for extraterrestrial life
(E) Propose that future research should focus on studying planetary systems around white dwarfs and pulsars
5. According to the passage, the supernova explosion that created PSR 1257+12 was:
(A) Caused by the collapse of a star approximately 20 times more massive than our sun
(B) Triggered by the gravitational influence of the planets now orbiting the pulsar
(C) Similar in scale and intensity to the event that will eventually destroy our own sun
(D) Responsible for ejecting most of the star's mass into the surrounding interstellar space
(E) Both A and D
6. The passage implies that the conservation of angular momentum is important in the formation of planetary systems because it:
(A) Causes the collapsing interstellar cloud to flatten into a disk shape
(B) Prevents all of the material in the disk from falling directly onto the newly formed star
(C) Determines the final masses and orbital distances of the planets that form in the disk
(D) Ensures that the planets will have stable, circular orbits around the central star
(E) Both A and B
7. The author's description of the planets orbiting PSR 1257+12 as having "risen up out of the ashes of the explosion" is meant to:
(A) Suggest that the planets were created from the debris left behind by the supernova
(B) Imply that the planets were able to survive the intense heat and radiation of the explosion
(C) Highlight the Phoenix-like rebirth of the planetary system after the destruction of the original star
(D) Propose that the planets were formed by a different process than those in our solar system
(E) Indicate that the composition of the planets is primarily made up of the heavy elements created in the supernova
8. Based on the information provided in the passage, which of the following statements about the pulsar PSR B1620-26 is most likely to be true?
(A) Its planet formed from the remnants of a supernova explosion, similar to the planets orbiting PSR 1257+12
(B) The planet's wide orbit suggests that it was captured from another star system rather than forming in a fallback disk
(C) The planet's existence was deduced from periodic deviations in the timing of the pulsar's radio pulses
(D) It is the only known example of a pulsar with a planetary companion in a distant orbit
(E) The discovery of this planet provided the first confirmation of the existence of extrasolar planets
9. The passage suggests that the study of extrasolar planetary systems has led astronomers to:
(A) Develop more sensitive instruments capable of detecting smaller and more distant planets
(B) Confirm the accuracy of planetary system formation models based on our own solar system
(C) Discover a greater variety of planetary systems than they had originally anticipated
(D) Focus their search for extraterrestrial life on planets orbiting stars similar to our sun
(E) Conclude that the conditions necessary for the formation of planets are relatively common in the universe
10. Which of the following best describes the overall structure of the passage?
(A) A description of a scientific discovery followed by an analysis of its implications and potential consequences
(B) A comparison of two competing theories and their ability to explain a set of observations
(C) An overview of a research field, highlighting recent discoveries and their impact on prevailing assumptions
(D) A narrative account of a series of scientific experiments and the challenges encountered by the researchers
(E) An argument for the importance of a particular area of research and its potential applications to other fields
1. 答案: C
解释: 作者在文章中多次表达了对extrasolar planetary systems多样性和适应性的惊讶,因此C选项最能描述作者的态度。
2. 答案: E
解释: 文章提到,脉冲星PSR 1257+12的行星很可能是在超新星爆发后从回落盘中形成的,因此E选项可以从文章信息中推断出来。
3. 答案: A
解释: 文章表明,白矮星和脉冲星上行星的发现挑战了行星最可能在类似太阳的恒星周围形成的假设,因此A选项是正确的。
4. 答案: D
解释: 作者的陈述旨在鼓励重新评估关于寻找外星生命的假设,因此D选项最准确。
5. 答案: E
解释: 文章提到,创造PSR 1257+12的超新星爆发是由一颗约20倍于太阳质量的恒星的坍塌引起的(A选项),并且大部分恒星的质量被喷射到周围的星际空间(D选项),因此E选项是正确的。
6. 答案: E
解释: 文章暗示角动量守恒在行星系统的形成中很重要,因为它会导致坍缩的星际云变成盘状(A选项),并阻止所有物质直接落到新形成的恒星上(B选项),因此E选项是正确的。
7. 答案: C
解释: 作者使用"从爆炸的灰烬中升起"这一描述,是为了强调行星系统在原恒星毁灭后的凤凰般的重生,因此C选项最恰当。
8. 答案: B
解释: 文章表明,PSR B1620-26的行星轨道很宽,表明它可能是从另一个恒星系统捕获的,而不是在回落盘中形成的,因此B选项最有可能正确。
9. 答案: C
解释: 文章表明,对extrasolar planetary systems的研究使天文学家发现了比他们原本预期更多样化的行星系统,因此C选项是正确的。
10. 答案: C
解释: 文章首先概述了extrasolar planetary systems研究领域的新发现,然后重点讨论了这些发现对主流假设的影响,因此C选项最准确地描述了文章的整体结构。
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发表于 2024-6-26 07:49:41
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