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Record-breaking quantum memory : one step closer to quantum internet [A] Two clouds of atoms that store quantum information, called quantum memories, have been connected across a longer distance than ever before. They could prove useful for building a quantum version of the internet . [B] Quantum communication relies on a phenomenon called entanglement. When a pair of particles or systems are quantum entangled, measuring one of them instantly influences the measured state of the other, regardless of the distance between them. [C] These connections can ’ t directly transfer information, because that would mean information is travelling faster than light, but entanglement can be used to create encrypted communications channels, secured against hacking by the laws of quantum physics. [D] Individual photons have been entangled across distances exceeding 1000 kilometres, but for larger systems of particles, which hold more information, maintaining this entanglement is harder. The maximum distance between a pair of entangled quantum memories so far is just 1.3 kilometres. [E] Xiao-Hui Bao at the University of Science and Technology of China and his colleagues have now smashed that record, entangling two quantum memories over 22 kilometres of fibre-optic cable installed underground. [F] Their quantum memories were each made of about 100 million extremely cold rubidium atoms in a vacuum chamber. The quantum state of each system of atoms was entangled with the state of a single photon, and the researchers sent those photons through the fibre-optic cables. [G] When a particular observation called a Bell measurement was performed on the two photons simultaneously, the quantum memories with which the photons were paired before the measurement became entangled to one another. [H] In a slightly different experiment using cables that weren ’ t installed underground but just coiled up in the lab, Bao and his team entangled quantum memories across 50 kilometres. [I] The end goal of this work is to create a quantum repeater that can receive and then retransmit quantum information so that it can be sent over long distances, eventually building up a secure internet of quantum information. [J] “ Honestly, there is still a long way to go in order to see the quantum repeater working in real long-distance situations, ” says Bao, but he thinks that building a small-scale prototype quantum network using quantum memories will be possible in the next few years. Questions 1- 5 Do the following statements agree with the information given in the above passage? TRUE if the statement agrees with the information FALSE if the statement contradicts the information NOT GIVEN if there is no information on this
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【单选题】Grandma, you must feel ________ after cleaning the house. Let’s take a rest.
A.
tired
B.
well
C.
good
D.
angry
【单选题】_______ we needn’t hurry, let’s take a rest.
A.
For
B.
Because
C.
Now
D.
While
【单选题】铺床时,床旁桌、床边椅距床适宜的距离是()。
A.
20cm,20cm
B.
20cm,15cm
C.
15cm,15cm
D.
15cm,20cm
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A.
刘少奇
B.
周恩来
C.
陈云
D.
邓子恢
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A.
刘少奇
B.
毛泽东
C.
陈云
D.
周恩来
【判断题】民间信用在方式上比较灵活、简便,可以随市调节居民个人之间的资金余缺,在一定范围内弥补了银行信用的不足,所以政府可以放开对其的监管 。
A.
正确
B.
错误
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A.
轻微事故
B.
一般事故
C.
重大事故
D.
较大事故
【单选题】更换动力电池箱散热器风扇时需要( )。
A.
行维修作业时需佩戴绝缘手套
B.
拆下维修开关把手前,应关闭点火钥匙,车辆静止5分钟以上,拆下蓄电池负极电缆
C.
将拆下的维修开关把手放在口袋内携带,以确保安全
D.
包括以上三项
【单选题】电梯轿厢困人时间超过 2 小时属于 __ 。
A.
轻微事故
B.
一般事故
C.
较大事故
D.
重大事故
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