THORLABS EDU-QCRY1 Manual

Quantum cryptography demonstration kit

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EDU-QCRY1

EDU-QCRY1/M

Quantum Cryptography

Demonstration Kit

Manual

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Summary of Contents for THORLABS EDU-QCRY1

Page 1 EDU-QCRY1 EDU-QCRY1/M Quantum Cryptography Demonstration Kit Manual...
Page 3 Table of Contents Chapter 1 Warning Symbols ................ 1 Chapter 2 Safety .................... 2 Chapter 3 Description ................... 3 Chapter 4 Components and Parts List ............5 Chapter 5 Fundamentals of Quantum Cryptography ........ 9 5.1. Introduction ................9 5.2. The One Time Pad ..............9 5.3.
Page 4 8.3. Adding Eve and Detection of Eavesdropping ......40 Chapter 9 Measuring Protocols ..............42 Chapter 10 Teaching Tips ................46 Chapter 11 Troubleshooting................. 47 Chapter 12 Acknowledgments ..............48 Chapter 13 Regulatory .................. 49 Chapter 14 Thorlabs Worldwide Contacts ..........50...
Page 5 Quantum Cryptography Demonstration Kit Chapter 1: Warning Symbols Chapter 1 Warning Symbols Below is a list of warning symbols you may encounter in this manual or on your device. Symbol Description Direct Current Alternating Current Both Direct and Alternating Current Earth Ground Terminal Protective Conductor Terminal Frame or Chassis Terminal...
Page 6 Quantum Cryptography Demonstration Kit Chapter 2: Safety Chapter 2 Safety WARNING The laser module is a class 2 laser. Although no protective eyewear is required around class 2 lasers, you should not look directly into the beam or into scattered light. ATTENTION To avoid contamination and damage, never touch the ��/2 plates with bare fingers.
Page 7 Quantum Cryptography Demonstration Kit Chapter 3: Description Chapter 3 Description Cryptography, the encryption of messages and data, has always been a fundamental topic in the field of communication. A wide variety of different methods were developed over the centuries in order to prevent decryption by third parties. However, all encryption methods have weaknesses;...
Page 8 Quantum Cryptography Demonstration Kit Chapter 3: Description repeated. Alice sends a bit, Eve tries to intercept it, and then Eve sends the bit to Bob in the basis that she had chosen for her measurement. At the end of the experiment, Alice and Bob compare their bases via a public exchange and also a few test bits.
Page 9 Quantum Cryptography Demonstration Kit Chapter 4: Components and Parts List Chapter 4 Components and Parts List In cases where the metric and imperial kits contain parts with different item numbers, metric part numbers and measurements are indicated by parentheses unless otherwise noted.
Page 10 Quantum Cryptography Demonstration Kit Chapter 4: Components and Parts List 7 x TR2 (TR50/M) 2 x RSP1X225(/M)-ALICE Ø1/2" (Ø12.7 mm) Post, 2" 2 x RSP1X225(/M)-BOB Ø1" Indexing Rotation (50 mm) Long Ø1" Indexing Rotation Mount, 22.5° steps Mount, 22.5° Steps 4 x WPH10E-633 2 x PM3(/M) ��/2 Plate, Zero Order...
Page 11 Quantum Cryptography Demonstration Kit Chapter 4: Components and Parts List 1 x BA1S(/M) Base, 1 x AT1(/M) 2 x CPS635R-C2 1" x 2.3" x 3/8" Alignment Tool 635 nm Laser Diode Module, (25 mm x 58 mm x 10 mm) 1.18"...
Page 12 Quantum Cryptography Demonstration Kit Chapter 4: Components and Parts List Imperial Kit Screws, Ball Driver, and Hex Keys Type Quantity Type Quantity 1/4"-20 x 3/8" Cap Screw 1/4" Washer 1/4"-20 x 1/2" Cap Screw 1/4"-20 x 5/8" Cap Screw 1/4"-20 x 1.25" Cap Screw 1 x BD-3/16L Balldriver for 1/4″-20 Screws 1/4"-20 x 2"...
Page 13 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography Chapter 5 Fundamentals of Quantum Cryptography This section explains how quantum cryptography works and the steps required to carry it out. It starts with a brief introduction and then explains the one-time pad which turns a message and a key into an encrypted message.
Page 14 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography The “calculation rules” that apply for binary addition are as follows: • 0 + 0 = 0 • 1 + 0 = 1 • 0 + 1 = 1 • 1 + 1 = 0 When the intended recipient obtains the encrypted message, they will use binary addition on the encrypted message and encryption key.
Page 15 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography To summarize the essential requirements: The key has to be at least as long as the message. The key must only be used once. The key must be completely random. The key must be known only to the sender and the recipient.
Page 16 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography Figure 2 Data Transmission with One Polarization Basis The sending unit “Alice” consists of a single photon source which is polarized horizontally and a ��/2 plate. The ��/2 plate rotates the polarization of the incident light by double the physical rotation angle of the wave plate.
Page 17 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography 5.3.2. Key Distribution – The Right Way While the method with one basis (0° or 90°) is sufficient to transfer data from Alice to Bob, it is not able to guarantee safety from interception. A second basis comes into play to accomplish this.
Page 18 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography In the table that follows, the different cases are shown again as an overview: Alice Same Detector “0” Detector “1” Basis Angle Basis Angle basis? 0° 0° 100% 90° 0° 100% 45°...
Page 19 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography 5.4. Detection of an Eavesdropper Let us examine the situation of an eavesdropper “Eve” placed between Alice and Bob. Eve consists of the same components as Alice and Bob, only in the reverse sequence. This is shown in Figure 4.
Page 20 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography Bob chooses the same basis as Alice: This case produces the error which allows Alice and Bob to detect Eve eavesdropping. Keep in mind that Alice and Bob have confirmed that they sent and received the signal using the same basis, so the measurement is not discarded.
Page 21 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography What Does “Random” Mean? 5.5. As described in Section 5.2, the one-time pad requires the completely random selection of the encryption key. This means computer-generated, pseudo-random numbers are not a solution for 100% security.
Page 22 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography 5.7. Experimental Procedure The sequence of steps for this experiment are taken from the the BB84 protocol. You can find the original publication here: http://researcher.watson.ibm.com/researcher/files/us-bennetc/BB84highest.pdf The sequence of the BB84 protocol experiment is: Alice chooses a random basis (x or +) and a bit (0 or 1).
Page 23 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography There are additional steps in the protocol, which are not implemented for this experiment: • Authentication: A few bits are exchanged at the start of communication according to a key established by Alice and Bob in advance. This step allows Alice to authenticate that she is communicating with Bob and not someone else.
Page 24 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography 5.10. Mathematical Description in Dirac Notation Up to here, we described the experiments qualitatively. The preparation of the polarization states and their measurement by Bob (and Eve) are comprehensive parts of the experimental realization.
Page 25 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography Due to symmetry it follows that �� = �� = 1/ √ 2. Therefore, all four states can be expressed | 45° ⟩ = | 0° ⟩ + | 90° ⟩ √...
Page 26 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography The diagonally polarized states behave accordingly when measured in the diagonal basis: �� ̂ | 45° ⟩ = | 45° ⟩⟨ 45° | 45°⟩ − | −45° ⟩⟨ −45° | 45°⟩ = | 45° ⟩ ×...
Page 27 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography Alice State Basis, Chosen State Measured Bit Basis �� ̂ | 0° ⟩ = |0°⟩ | 0° ⟩ +, 0 �� ̂ | 0° ⟩ = | 45° ⟩ − | −45°...
Page 28 Quantum Cryptography Demonstration Kit Chapter 5: Fundamentals of Quantum Cryptography Alice Basis, State Basis State State Basis State Measured Sent �� ̂ | 0° ⟩ = |0°⟩ �� ̂ | 0° ⟩ = |0°⟩ |0°⟩ �� ̂ | 0° ⟩ = | 45°...
Page 29 Quantum Cryptography Demonstration Kit Chapter 6: Examples Chapter 6 Examples 6.1. Encryption Protocol without Eve (Two Letters) Step 1: Alice and Bob randomly select their bases, and Alice also selects her bits Alice Basis Basis Step 2: Alice sends the bits in the chosen basis and Bob records the bits he measures. During Bob's measurements, he uses the bases chosen randomly by him.
Page 30 Quantum Cryptography Demonstration Kit Chapter 6: Examples The resulting key generated by the two of them is: “0 1 1 0 0 1 0 0 0 1”. Both know this key even though they have only exchanged their bases. Step 4: Alice encrypts two letters with the key that was just generated. Read the binary representation of Q and M from the alphabet table, then perform binary addition on the first and second rows, see Chapter 9 for reference tables.
Page 31 Quantum Cryptography Demonstration Kit Chapter 6: Examples 6.2. Encryption Protocol with Eve The process of generating the key is discussed again here, but this time with Eve who is eavesdropping. Her presence is discovered by comparing test bits. Step 1: Alice, Bob and Eve randomly select their bases, and Alice also randomly selects bits to send.
Page 32 Quantum Cryptography Demonstration Kit Chapter 6: Examples Step 2: Alice then sends the bits using her selected basis and Bob records the bits he measures. However, in this scenario, Eve is between Alice and Bob and selects her basis randomly as well (either 0° and 45°). If Eve's basis matches the one chosen by Alice, Eve will transmit the correct bit.
Page 33 Quantum Cryptography Demonstration Kit Chapter 6: Examples Step 3: At this point, Alice and Bob exchange the bases used for transmitting and receiving (“I have +” or “I have x”). They highlight the measurements where the bases match. Alice Basis Basis Step 4: Now Alice and Bob compare the bits for which their bases matched (the ones circled in red)
Page 34 Quantum Cryptography Demonstration Kit Chapter 7: Setup and Adjustment Chapter 7 Setup and Adjustment 7.1. Component Assembly Screw the RDF1 feet onto all breadboards. To do this, use the 1/4"-20 x 1/2" (M6 x 12 mm) screws to secure four feet to the bottom of each breadboard. Take a BA1(/M) base and Take a BA1S(/M) base Take a BA1(/M) base and...
Page 35 Quantum Cryptography Demonstration Kit Chapter 7: Setup and Adjustment Now set up the two beamsplitters: Use the UPH2 (UPH50/M) universal holder and insert a TR2 (TR50/M) post. Remove the set screw from the post with a hex key. Attach the KM100PM/M with a included cap screw.
Page 36 Quantum Cryptography Demonstration Kit Chapter 7: Setup and Adjustment 7.2. Electronics 7.2.1. Power Supply The power supply included in this kit is designed to provide a stabilized 5 V. Select the correct plug for your region and insert it in the jack on the power supply. 7.2.2.
Page 37 Quantum Cryptography Demonstration Kit Chapter 7: Setup and Adjustment 7.2.3. Sensor Electronics The sensor electronics have a connection for the power supply and two sensor inputs. A sensor can be plugged into either of the two sensor ports. Ensure that the sensors are connected to the electronics box prior to inserting the power supply.
Page 38 Quantum Cryptography Demonstration Kit Chapter 7: Setup and Adjustment Use the AT1/M height adjustment tool to ensure that the laser runs parallel to the tabletop. Adjust the laser tip/tilt using the adjusters on the KM100 mount, if necessary. To ensure the best alignment, use the AT1/M adjustment tool alternating between close and far distances from the laser during the alignment process.
Page 39 Quantum Cryptography Demonstration Kit Chapter 7: Setup and Adjustment Rotate the ��/2 plate and observe the reflected intensity. The intensity will vary with the rotation angle. Look for the orientation with the lowest reflected intensity. Once you’ve found the angle which minimizes the intensity of the reflected light, engage the indexing mode by tightening the screw at the top of the rotation mount.
Page 40 Quantum Cryptography Demonstration Kit Chapter 7: Setup and Adjustment 7.4. Setup for Alice and Bob Alice and Bob should face each other at a distance of about 60 cm. For best performance, set up the two breadboards up as parallel as possible. •...
Page 41 Quantum Cryptography Demonstration Kit Chapter 7: Setup and Adjustment That the sensor is at the correct height. That the laser light is centered on the hole in the sensor module. If difficulties are encountered, have one user continue sending pulses with the laser while the other aligns the sensor.
Page 42 Quantum Cryptography Demonstration Kit Chapter 7: Setup and Adjustment 7.5. Adding Eve To add Eve as an eavesdropper to the setup, place the large breadboard between the breadboards of Alice and Bob. In this scenario, Eve is intended to intercept transmissions from Alice to Bob, so avoid making changes to Alice and Bob and align Eve within the setup.
Page 43 Quantum Cryptography Demonstration Kit Chapter 8: Experiment Chapter 8 Experiment The experiment is divided into three sections: • Section 8.1: Generating a key with a length of at least 20 bits • Section 8.2: Encryption and transmission of a 4-letter word •...
Page 44 Quantum Cryptography Demonstration Kit Chapter 8: Experiment Exercise 4: Alice and Bob publically exchange the bases used for each measurement. They then erase any measurements where the bases do not match. The remaining measurements/bits form the complete encryption key. Execution: This corresponds to step 3 in the example detailed in Section 6.1. Alice and Bob exchange their bases (“I have chosen +”...
Page 45 Quantum Cryptography Demonstration Kit Chapter 8: Experiment Eve's operator. Choosing random bases at the start of the sequence prevents this bias from interfering with the results of the experiment. A sample table of bases for Eve to use can be found in Chapter 9. Keep in mind that Eve's operator does not have to record any data.
Page 46 In order to make them easy to print, each of them is on one page (the manual is also available as a free download at discovery.thorlabs.com). Then you find the table with the encoding of the alphabet using 5 bits per letter.
Page 47 Quantum Cryptography Demonstration Kit Chapter 9: Measuring Protocols Measuring protocol for key generation – ALICE Basis (+ or x) (0 or 1) Basis (+ or x) (0 or 1) Basis (+ or x) (0 or 1) Generated Key: Angle Basis + Basis x setting _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _...
Page 48 Quantum Cryptography Demonstration Kit Chapter 9: Measuring Protocols Measuring protocol for key generation – BOB Basis (+ or x) (0 or 1) Basis (+ or x) (0 or 1) Basis (+ or x) (0 or 1) Generated Key: Reminder transmitted reflected _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Basis +...
Page 49 Quantum Cryptography Demonstration Kit Chapter 9: Measuring Protocols Basis selection – EVE Basis (+ or x) Basis (+ or x) Basis (+ or x) Binary representation of the alphabet Binary Addition Table MTN005660-D02 Page 45...
Page 50 Quantum Cryptography Demonstration Kit Chapter 10: Teaching Tips Chapter 10 Teaching Tips The generation of random numbers is a fundamental problem in quantum cryptography. When the selection of bases and bits in the experiment is performed with human- generated random numbers, Alice and Bob may have a lot of matches because a human is a poor random number generator.
Page 51 Quantum Cryptography Demonstration Kit Chapter 11: Troubleshooting Chapter 11 Troubleshooting When running through the 8 combinations of the ��/2 plates of Alice and Bob (or Alice and Eve, Eve and Bob), not all 8 cases work. • Are both sensor electronics boxes set to the adjustment mode? This is indicated by the LED on the side emitting yellow light.
Page 52 Quantum Cryptography Demonstration Kit Chapter 12: Acknowledgments Chapter 12 Acknowledgments This experiment package was developed in close cooperation with various lecturers dedicated to the teaching of quantum physics. We would like to express our sincere appreciation to: • OStR Jörn Schneider, Leibniz-Gymnasium Dormagen,...
Page 53 Waste Treatment is Your Own Responsibility If you do not return an “end of life” unit to Thorlabs, you must hand it to a company specialized in waste recovery. Do not dispose of the unit in a litter bin or at a public waste disposal site.
Page 54 Quantum Cryptography Demonstration Kit Chapter 14: Thorlabs Worldwide Contacts Chapter 14 Thorlabs Worldwide Contacts For technical support or sales inquiries, please visit us at www.thorlabs.com/contact our most up-to-date contact information. USA, Canada, and South America UK and Ireland Thorlabs, Inc.
Page 56 www.thorlabs.com...

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