Create an Account  |   Log In

View All »Matching Part Numbers


Your Shopping Cart is Empty
         

Quantum Cryptography Analogy Demonstration Kit


  • Designed for Education, Demonstration, and Classroom Use
  • Easy-to-Use Kits Include Components Plus Educational Materials
Related Items


Please Wait

Click to Enlarge

Binary information encoded in the polarization state of light is detected by a sensor module (indicated by a blue LED). 
Download Educational Materials

Quantum Cryptography Analogy Demonstration Kit

  • Designed for Educational, Demonstration, and Classroom Use
  • Complete Photonics Kit Includes All Hardware Plus Extensive Manual and Teaching Materials
  • Easy to Assemble and Use
  • Choose from Educational Kits Containing Imperial or Metric Components

Experiment

  • Learn How Information Can Be Encrypted and Sent Using the Polarization of Light
  • Generate an Encryption Key that Allows for Private Communication
  • Encrypt, Transmit, and Decrypt a Secret Message
  • Examine How an Eavesdropper Causes Errors in Transmission that Can Be Detected
  • Demonstrate the Steps of the BB84 Encryption Protocol

The EDU-QCRY1(/M) Quantum Cryptography Analogy Demonstration Kit contains components to model a data transmission setup using the BB84 encryption protocol. This encryption method allows a sender and receiver to generate an encryption key that only they know and eavesdroppers to be detected. In this analogy experiment, the polarization of transmitted light carries bits of information which are manipulated using half-wave plates and polarizing beamsplitters. The educational lab kit includes the lasers, half-wave plates, polarizing beamsplitters, and detectors required to model the sender (Alice), the receiver (Bob) and the eavesdropper (Eve).

Please note that this is a classical experiment that simulates the key principles used in quantum cryptography. As an analogy to the quantum setup, this experiment works with a pulsed laser instead of single photons. Single photon detectors are not included in this kit.

Thorlabs Educational Products

Thorlabs' line of educational products aims to promote physics, optics, and photonics by covering many classic experiments, as well as emerging fields of research. Each educational kit includes all the necessary components and a manual that contains both detailed setup instructions and extensive teaching materials. These lab kits are being offered at the price of the included components, with the educational materials offered for free. Technical support from our educational team is available both before and after purchase.

Purchasing Note: English and German language manuals/teaching information are available for this product. The imperial educational kit contains the English manual and US-style power cords. The appropriate manual and power cords will be included in the metric kit based on your shipping location. The power supplies and other electronic devices in both the metric and the imperial kit accept voltages of 230 VAC and 120 VAC. Please contact Tech Support if you need a different language, cord style, or power supply. As with all products on our website, taxes are not included in the price shown below.

This kit is designed to demonstrate the fundamentals of quantum cryptography and the BB84 encryption protocol through a series of classroom experiments. In these experiments, students will learn how to encode messages in binary using the polarization state of light and then encrypt them using the BB84 protocol.

The BB84 Protocol
The BB84 protocol is a communication scheme that combines an encryption technique known as the one-time pad with a quantum key distribution method. Message encryption using the one-time pad method is accomplished by adding a binary encryption key (consisting of 0s and 1s) to a message represented in binary. Because there is no methodology or pattern to the key or message, this method of encryption ensures that the encrypted message can be transmitted through public channels.

However, the fundamental challenge is ensuring that only Alice and Bob have knowledge of the encryption key and preventing an eavesdropper (designated as Eve) from intercepting the encryption key. The BB84 encryption protocol uses the idea of quantum key distribution (QKD) to ensure that only Alice and Bob have knowledge of the encryption key. QKD employs principles of quantum physics, such as the encoding of a single bit of information within a photon of light, to ensure that the information cannot be copied. Any interception attempt by Eve will inevitably change the state of the photon. Thus, the BB84 protocol offers the ability to send truly secure encrypted transmissions.

Modeling the BB84 Protocol Using the Polarization of Light
The EDU-QCRY1(/M) kit models the BB84 method using the polarization states of light (as illustrated in the diagram below). Data in the form of a bit is encoded into a pulsed laser beam by altering the polarization state. More specifically, the bit is encoded using a basis polarization pair (represented as a + or x) which converts the bit into a specific polarization angle. The + basis is represented by 0° and 90° polarizations while the x basis is represented by -45° and 45° polarizations. One of the polarizations in each pair represents a "0" bit while the other represents a "1" bit. Alice performs a transmission by emitting a pulsed beam of light and setting the polarization state with a half-wave plate to encode the bit and basis. The receiver (Bob) is equipped with a half-wave plate and beamsplitter to interpret the transmission as either a "0" or "1". The bits and bases are randomly chosen in each transmission; however by comparing bases, Alice and Bob can generate a unique encryption key only known to each other. 

In this experiment, the eavesdropper (Eve) is represented by a module that can receive a transmission from Alice and then attempt to send the same signal to Bob. While Eve is free to do this since the "transmission" is public, students will learn how this will cause errors that reveal the presence of an eavesdropper. Because detection of an eavesdropper occurs during transmission of the encryption key, once Alice and Bob have verified that there is no eavesdropper, the message can be sent without risk of interception. 


This schematic illustrates the Alice, Eve, and Bob modules of the EDU-QCRY(/M) Quantum Cryptography Kit. The polarization state of light is changed by the polarization rotators to encode a "1" or "0" in a specific basis for transmission. The light is received by another polarization rotator, which allows the beamsplitter to send the light to the appropriate sensor for detection.

Single Photons Versus Classical Light
Genuine safety from an eavesdropper is only guaranteed if the BB84 protocol is carried out using single photons, which obey the “no cloning theorem”. In general, this theorem states a perfect copy of an unknown quantum state cannot be made without altering the state. As a result, Eve cannot copy a photon from Alice without altering it and cannot send an unaltered photon to Bob while keeping a copy for analysis.

Please note that the EDU-QCRY1(/M) analogy kit uses a pulsed laser source, i.e. classical light. While the sequence of the protocol is completely identical to the true quantum encryption system, it cannot be used as a perfect encryption system. Eve is able to eavesdrop unnoticed by separating a portion of the transmitted light for analysis while the remainder is sent to Bob.

This tab illustrates an example exercise that can be done by students using the EDU-QCRY1(/M) Quantum Cryptography Analogy Demonstration Kit. For full details on exercises and worksheets for students, please refer to the manual.

Basis Bit Polarization
+ 0
1 90°
× 0 -45°
1 45°

This example illustrates the generation of an encryption key between Alice and Bob, and the transmission a 10-bit, two-letter encrypted message using the BB84 protocol. 

Generating an Encryption Key
First, Alice will randomly choose a sequence of bits and a bases (either + or ×) for the key transmission. The combination of bit and basis determines the polarization of the pulse of light transmitted by Alice (see the table to the right for possible combinations). Table 1 shows a sequence of 18 randomly chosen bits and bases, and the corresponding polarization angle. For further details on how to determine the polarization angle, please refer to the manual.

Table 1: Transmitting (Alice)
Index 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Alice's Basis (Random) × × + × + + + × × + × × × + + × + ×
Alice's Bit (Random) 1 0 0 1 1 0 0 1 1 1 0 1 0 0 0 1 0 1
Polarization Angle 45° -45° 45° 90° 45° 45° 90° -45° 45° -45° 45° 45°

At the same time, Bob chooses a random set of bases to use in receiving the transmission. These bases are chosen independently from Alice and will not always match. After transmission, Alice and Bob compare bases that they used. In cases where the basis matches with the one chosen by Alice (highlighted in green in Table 2), Bob will obtain the same bit as chosen by Alice. However, if the basis does not match, Bob will randomly receive a 0 or 1. Because the result is random, these bits are thrown out; the remaining green-highlighted bits become the encryption key between Alice and Bob.

Table 2: Receiving (Bob)
Index 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Bob's Basis (Random) + × × × + + + × + × × + + × + + + ×
Bob's Bit (From Alice) 1 0 1 1 1 0 0 1 1 1 0 1 0 1 0 0 0 1

In this example, the encryption key would be the sequence: "0 1 1 0 0 1 0 0 0 1".

Sending an Encrypted Message Using an Encryption Key
Now we will illustrate how to send a two-letter message "QM" using the encryption key above. First, each letter is converted into a 5-bit binary representation, as shown in Table 3 (see Chapter 9 of the manual for a reference table with binary representations for the full alphabet). While this example uses binary format to send alphabetical letters, any kind of information could theoretically be encoded into a binary sequence.

To encrypt the message, Alice performs binary addition on the message and encryption key (see the table below for addition rules). The resulting 10-bit message can then sent from Alice to Bob through public channels and using a previously agreed upon basis (i.e., Alice and Bob both choose to use either a + or × basis). After transmission, Bob can then decode the message by using binary addition on the encrypted message key using the encryption key. Because the results of binary addition are reversible, adding in this fashion returns the original binary message.

Table 3: Sending an Encrypted Message
Lettera Q M
Binary Message 1 0 0 0 0 0 1 1 0 0
Encryption Key 0 1 1 0 0 1 0 0 0 1
Encrypted Messageb 1 1 1 0 0 1 1 1 0 1
  • In this example, a letter is expressed in terms of a 5-bit sequence. A reference table for the entire alphabet is included in Chapter 9 of the manual.
  • The encrypted message is generated by binary addition of the message and key.
Binary Addition Rules
0 + 0 = 0
0 + 1 = 1
1 + 0 = 1
1 + 1 = 0

This method for sending secure messages, however, assumes that no eavesdropper has knowledge of the encryption key. Because the transmissions described above are carried out via public channels, Eve can try to intercept the encryption key by intercepting the transmission between Alice and Bob. However, doing so will cause errors in the transmission. In the BB84 protocol, after comparing bases (Table 2), Alice and Bob will compare a test region of the encryption key. The errors introduced by Eve can be found by Alice and Bob when comparing the test region, alerting them to the presence of the eavesdropper. For a more detailed example, see Section 6.2 of the manual.

Quantum Cryptography Analogy Demonstration Kit Components

Thorlabs' Quantum Cryptography Analogy Demonstration Kit is available in imperial and metric versions. In cases where the metric and imperial kits contain parts with different item numbers, metric part numbers are listed next to their imperial counterpart and measurements are indicated in parenthesis.

Kit Components
EDU-QCRY1
Item #
EDU-QCRY1/M
Item #
Description Qty.
MB8 MB2020/M Aluminum Breadboard
8" x 8" (20 cm x 20 cm)
1
MB810 MB2025/M Aluminum Breadboard
8" x 10" (20 cm x 25 cm)
1
MB1218 MB3045/M Aluminum Breadboard
12" x 18" (30 cm x 45 cm)
1
BA1 BA1/M Post Holder Base 10
PH2 PH50/M Post Holder, 2" (50 mm) Long 5
PH1.5 PH40/M Post Holder, 1.5" (40 mm) Long 6
UPH2 UPH50/M Universal Post Holder, 2" (50 mm) Long 2
TR1.5 - Optical Post, 1.5" Long 6
- TR30/M Optical Post, 30 mm Long 4
- TR40/M Optical Post, 40 mm Long 2
TR2 TR50/M Optical Post, 2" (50 mm) Long 7
RSP1X225-ALICEa RSP1X225/M-ALICEa Ø1" Indexing Rotation Mount, 22.5° Steps 2
RSP1X225-BOBa RSP1X225/M-BOBa Ø1" Indexing Rotation Mount, 22.5° Steps 2
PM3 PM3/M Clamping Arm 2
BA1S BA1S/M Swivel Post Holder Base 1
  • These parts are based on the RSP1X225, but feature a custom dial face designed for use in these kits.
Kit Components
EDU-QCRY1 Item # EDU-QCRY1/M Item # Description Qty.
AT1 AT1/M Alignment Tool 1
CL3 CL3/M Compact Variable Height Clamp 2
N/A N/A Kinematic Platform Mounta 2
RDF1 Rubber Damping Feet (4 Pack) 3
WPH10E-633 Zero-Order Half-Wave Plate 4
KM100 Ø1" Kinematic Mount 2
PBS201 Polarizing Beamsplitter Cube 2
AD11NT Ø1" Adapter for Ø11 mm Components 2
CPS635R-C2b 635 nm Laser Diode Module 2
BBH1 Breadboard Handles 1
SPW606 SM1 (1.034"-40) Spanner Wrench 1
N/A Sensor Module 4
N/A Sensor Electronics Module 2
N/A Laser Electronics Module 2
N/A 5 V Power Supply 4
  • These parts are a custom version of the KM100PM(/M).
  • This part is a class 2 version of the CPS635R.

Imperial Kit: Included Hardware and Screws

Item # Description Qty. Item # Description Qty.
BD-3/16L 3/16" Balldriver 1 - 1/16" Hex Key 1
- 1/8" Hex Key 1 - 3/32" Hex Key 1
W25S050 1/4" Washer 19 SH25S038 1/4"-20 Cap Screw,
3/8" Long
11
SH25S050 1/4"-20 Cap Screw,
1/2" Long
12 SH25S063 1/4"-20 Cap Screw,
5/8" Long
17
- 1/4"-20 Cap Screw,
1.25" Long
2 SH25S200 1/4"-20 Cap Screw,
2" Long
2
AS4M8E M4 to 8-32 Thread Adapter 4 - - -

Metric Kit: Included Hardware and Screws

Item # Description Qty. Item # Description Qty.
BD-5ML 6 mm Balldriver 1 - 1.5 mm Hex Key 1
- 2 mm Hex Key 1 - 3 mm Hex Key 1
W25S050 M6 Washer 19 SH6MS10 M6 Cap Screw,
10 mm Long
11
SH6MS12 M6 Cap Screw,
12 mm Long
12 SH6MS16 M6 Cap Screw,
16 mm Long
17
- M6 Cap Screw,
30 mm Long
2 - M6 Cap Screw,
45 mm Long
2

The EDU-QCRY1(/M) was developed in cooperation with several educators and organizations specializing in teaching quantum physics:

  • Jörn Schneider, Leibniz-Gymnasium Dormagen
  • Jan-Peter Meyn and Andreas Vetter, University Erlangen-Nuremberg (www.quantumlab.de)
  • Quantum Physics in School 2014 Meeting, Munich (www.heisenberg-gesellschaft.de)

Do you have ideas for an experiment that you would like to see implemented in an educational kit? Contact us at techsupport@thorlabs.com; we'd love to hear your ideas.

Laser Safety and Classification

Safe practices and proper usage of safety equipment should be taken into consideration when operating lasers. The eye is susceptible to injury, even from very low levels of laser light. Thorlabs offers a range of laser safety accessories that can be used to reduce the risk of accidents or injuries. Laser emission in the visible and near infrared spectral ranges has the greatest potential for retinal injury, as the cornea and lens are transparent to those wavelengths, and the lens can focus the laser energy onto the retina. 

Laser Glasses Laser Curtains Blackout Materials
Enclosure Systems Laser Viewing Cards Alignment Tools
Shutter and Controllers Laser Safety Signs

Safe Practices and Light Safety Accessories

  • Thorlabs recommends the use of safety eyewear whenever working with laser beams with non-negligible powers (i.e., > Class 1) since metallic tools such as screwdrivers can accidentally redirect a beam.
  • Laser goggles designed for specific wavelengths should be clearly available near laser setups to protect the wearer from unintentional laser reflections.
  • Goggles are marked with the wavelength range over which protection is afforded and the minimum optical density within that range.
  • Laser Safety Curtains and Laser Safety Fabric shield other parts of the lab from high energy lasers.
  • Blackout Materials can prevent direct or reflected light from leaving the experimental setup area.
  • Thorlabs' Enclosure Systems can be used to contain optical setups to isolate or minimize laser hazards.
  • A fiber-pigtailed laser should always be turned off before connecting it to or disconnecting it from another fiber, especially when the laser is at power levels above 10 mW.
  • All beams should be terminated at the edge of the table, and laboratory doors should be closed whenever a laser is in use.
  • Do not place laser beams at eye level.
  • Carry out experiments on an optical table such that all laser beams travel horizontally.
  • Remove unnecessary reflective items such as reflective jewelry (e.g., rings, watches, etc.) while working near the beam path.
  • Be aware that lenses and other optical devices may reflect a portion of the incident beam from the front or rear surface.
  • Operate a laser at the minimum power necessary for any operation.
  • If possible, reduce the output power of a laser during alignment procedures.
  • Use beam shutters and filters to reduce the beam power.
  • Post appropriate warning signs or labels near laser setups or rooms.
  • Use a laser sign with a lightbox if operating Class 3R or 4 lasers (i.e., lasers requiring the use of a safety interlock).
  • Do not use Laser Viewing Cards in place of a proper Beam Trap.

 

Laser Classification

Lasers are categorized into different classes according to their ability to cause eye and other damage. The International Electrotechnical Commission (IEC) is a global organization that prepares and publishes international standards for all electrical, electronic, and related technologies. The IEC document 60825-1 outlines the safety of laser products. A description of each class of laser is given below:

Class Description Warning Label
1 This class of laser is safe under all conditions of normal use, including use with optical instruments for intrabeam viewing. Lasers in this class do not emit radiation at levels that may cause injury during normal operation, and therefore the maximum permissible exposure (MPE) cannot be exceeded. Class 1 lasers can also include enclosed, high-power lasers where exposure to the radiation is not possible without opening or shutting down the laser.  Class 1
1M Class 1M lasers are safe except when used in conjunction with optical components such as telescopes and microscopes. Lasers belonging to this class emit large-diameter or divergent beams, and the MPE cannot normally be exceeded unless focusing or imaging optics are used to narrow the beam. However, if the beam is refocused, the hazard may be increased and the class may be changed accordingly.  Class 1M
2 Class 2 lasers, which are limited to 1 mW of visible continuous-wave radiation, are safe because the blink reflex will limit the exposure in the eye to 0.25 seconds. This category only applies to visible radiation (400 - 700 nm).  Class 2
2M Because of the blink reflex, this class of laser is classified as safe as long as the beam is not viewed through optical instruments. This laser class also applies to larger-diameter or diverging laser beams.  Class 2M
3R Lasers in this class are considered safe as long as they are handled with restricted beam viewing. The MPE can be exceeded with this class of laser, however, this presents a low risk level to injury. Visible, continuous-wave lasers are limited to 5 mW of output power in this class.  Class 3R
3B Class 3B lasers are hazardous to the eye if exposed directly. However, diffuse reflections are not harmful. Safe handling of devices in this class includes wearing protective eyewear where direct viewing of the laser beam may occur. In addition, laser safety signs lightboxes should be used with lasers that require a safety interlock so that the laser cannot be used without the safety light turning on. Class-3B lasers must be equipped with a key switch and a safety interlock.  Class 3B
4 This class of laser may cause damage to the skin, and also to the eye, even from the viewing of diffuse reflections. These hazards may also apply to indirect or non-specular reflections of the beam, even from apparently matte surfaces. Great care must be taken when handling these lasers. They also represent a fire risk, because they may ignite combustible material. Class 4 lasers must be equipped with a key switch and a safety interlock.  Class 4
All class 2 lasers (and higher) must display, in addition to the corresponding sign above, this triangular warning sign  Warning Symbol

Posted Comments:
mike antunes  (posted 2020-10-18 13:29:49.597)
Could i get more information on this kit? I not sure how to send a message. thanks mike
cyasar  (posted 2018-02-14 13:31:00.61)
Hello I am Cumali YAŞAR; I am a Ph.D. student at Çanakkale Onsekiz Mart University. I wrote a project on Quantum Key Distribution. The budget is low. We decided to buy "Quantum Cryptography Demonstration Kit" as a team. We need some information from you guys. Question -1: Do you send the technical specifications for the purchase? Question 2: Can the Quantum Cryptography Demonstration Kit be controlled by a computer? How do we get the results of the squeeze process. We thank you.
jkuchenmeister  (posted 2018-02-14 10:07:57.0)
This is a response from Jens at Thorlabs: Question 1: I'll get in touch with you via e-mail. Question 2: At the moment, the experiment does not feature a computer control. The laser pulses are released manually. The information which detector responds is given by the signal LEDs at the top of the sensor units. Please note that there is no squeeze process. The kit is a purely classical demonstration kit with a pulsed laser. There is no actual quantum physics going on. However, since the polarization state of light is similar for a classical wave and single photons, students can go through the whole BB84 protocol (preparation of the state, measurement, etc.) to understand this protocol of quantum cryptography.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available
EDU-QCRY1 Support Documentation
EDU-QCRY1Quantum Cryptography Analogy Demonstration Kit, Imperial
$3,547.21
Today
+1 Qty Docs Part Number - Metric Price Available
EDU-QCRY1/M Support Documentation
EDU-QCRY1/MQuantum Cryptography Analogy Demonstration Kit, Metric
$3,547.21
Today
Log In  |   My Account  |   Contact Us  |   Careers  |   Privacy Policy  |   Home  |   FAQ  |   Site Index
Regional Websites: West Coast US | Europe | Asia | China | Japan
Copyright © 1999-2020 Thorlabs, Inc.
Sales: 1-973-300-3000
Technical Support: 1-973-300-3000


High Quality Thorlabs Logo 1000px:Save this Image