Quantum Audio

An open-source Python package for building Quantum Representations of Digital Audio using Qiskit circuits.

💿 What is Quantum Audio ?

Quantum audio refers to the application of principles from quantum mechanics to the creation, processing, and analysis of sound or audio signals.

Here, the information is processed using quantum bits, or qubits, instead of classical bits (0s and 1s). Unlike classical bits which can only be in one state at a time, qubits can exist in multiple states at once until they are measured.

New Paradigm 🎵

Audio plays a vital role in carrying information and music, traversing through domains — from Analog and Digital formats to engaging our senses in a profound way. With the advent of Quantum Computing, Quantum Audio formulate ways of representing Audio in the Quantum Domain, enabling new explorations in artistic and research contexts 💫

The Package 📦

The quantumaudio package provides fundamental operations for representing audio samples as Quantum States that can be processed on a Quantum computer (or a Simulator) and played back 🔊

quantumaudio.encode(audio)   # returns a quantum circuit
quantumaudio.decode(circuit) # returns audio samples

Quantum Audio represents Audio in terms of Quantum Circuits and does not require Quantum Memory for storage.

🗒️ Table of Contents

• Overview
• Version Information
• Installation
• Usage
• Additional Resources
• Contributing
• Future Releases
• Citing
• Contact

🔍 Overview

Modulation Schemes are essential methods for encoding Audio signals in both Analog (such as FM 📻) and Digital (such as PCM 💻) formats. The same is extended for Quantum Audio. The package contains different schemes to encode audio and necessary utilities.

The following subpackages can be accessed from quantumaudio:

• schemes: Quantum Audio Representation Methods. The following are included in the package:

Acronym	Representation Name	Original Reference
QPAM	Quantum Probability Amplitude Modulation	Real-Ket
SQPAM	Single-Qubit Probability Amplitude Modulation	FRQI
MSQPAM	Multi-channel Single-Qubit Probability Amplitude Modulation	PMQA
QSM	Quantum State Modulation	FRQA
MQSM	Multi-channel Quantum State Modulation	QRMA

• utils : Common utilary functions for data processing, analysis, circuit preparation, etc.

Additionally, tools contain extension functions that support basic visual analysis and audio processing.

For a quick tour of Quantum Audio, try Colab 🚀

Documentation

For more details of the package and its modules, please refer to the Documentation site.

🧩 Version Information

Pre-release original version: v0.0.2

This project is derived from research output on Quantum Representations of Audio, carried by Interdisciplinary Centre for Computer Music Research (ICCMR), University of Plymouth, UK, namely:

• Itaboraí, P.V., Miranda, E.R. (2022). Quantum Representations of Sound: From Mechanical Waves to Quantum Circuits. In: Miranda, E.R. (eds) Quantum Computer Music. Springer, Cham. https://doi.org/10.1007/978-3-031-13909-3_10

• Itaboraí, P. V. (2022). Quantumaudio Module (Version 0.0.2) [Computer software]. https://github.com/iccmr-quantum/quantumaudio

• Itaboraí, P. V. (2023) Towards Quantum Computing for Audio and Music Expression. Thesis. University of Plymouth. Available at: https://doi.org/10.24382/5119

For more details, see the NOTICE file.

Redevelopment: v0.1.0

This project has been completely re-developed and is now maintained by Moth Quantum.

• New Architecture:

  • This project has been restructured for better flexibility and scalability.
  • Instead of QuantumAudio Instances, the package begins at the level of Scheme Instances that perform encoding and decoding functions independent of the data.

• Feature Updates:

  • Introducing 2 Additional Schemes that can encode and decode Multi-channel Audio.
  • Supports Faster encoding and decoding of long audio files using Batch processing.

• Dependency Change:

  • Support for Qiskit is updated from v0.22 to v1.0+

• Improvements:

  • Improved organisation of code for Readability and Modularity.
  • Key metadata information is preserved during the encoding operation, making the decoding process independent.

• License Change:

  • The License is updated from MIT to Apache 2.0

Migration Guide

If you're transitioning from the previous version, please check the Migration Guide for an overview of the package usability.

🪄 Installation

To install the Quantum Audio Package, you can use pip (included with Python) which installs it from PyPI package manager. Run the following command in Terminal or Command Prompt:

pip install quantumaudio

For local installation by cloning, navigate to the cloned directory in Terminal or Command Prompt and run:
pip install . or pip install -r requirements.txt

Note

When using pip commands to install packages and dependencies, it's recommended to use a virtual environment to keep them isolated from the system's Python. This will avoid any dependency conflicts. Instructions on using a virtual environment are provided here.

Optional Dependencies

All additional dependencies required that support the demos provided in the repository can be installed using pip:

pip install "quantumaudio[demos]"

It includes the following collection of dependencies, also mentioned in the folder demos/requirements:

• Digital Audio Dependencies The core package operates with numpy arrays. Dependencies for audio file handling to run audio examples in notebook and scripts in the repository can be separately installed using pip install soundfile==0.12.1 librosa==0.10.2.post1

Tip

If using your own choice of libraries for digital audio processing, please be aware that Multi-channel Quantum Audio is processed with Channels First data structure. e.g. (2, N) for a Stereo Audio of N samples.

• Notebook Dependencies The Demo Notebook features interactive elements that require additional dependency. It can be installed using pip install ipywidgets

🎛️ Usage

Using Schemes

Get started on creating Quantum Audio Representations with just a few lines of code.

# An instance of a scheme can be created using:
import quantumaudio
qpam = quantumaudio.load_scheme("qpam") # or directly access from quantumaudio.schemes.QPAM()

# Define an Input
original_data = quantumaudio.tools.test_signal() # for a random array of samples (range: -1.0 to 1.0)

# Encoding
encoded_circuit = qpam.encode(original_data)

# ... optionally do some analysis or processing

# Decoding
decoded_data  = qpam.decode(encoded_circuit,shots=4000)    

Note

The encode function returns a circuit with attached classical measurements by default. In Qiskit, it is not possible to directly modify a circuit after these measurements are added. If you wish to return a circuit without measurements, you can specify measure=False while encoding.

Using Functions

The core functions are also directly accessible without declaring a Scheme object. (Refer to Documentation for all the available functions)

circuit = quantumaudio.encode(data, scheme="qpam")
decoded_data = quantumaudio.decode(circuit)

Here, any remaining arguments can be passed as keywords e.g. quantumaudio.encode(data, scheme="qsm", measure="False").

Note

The circuit depth can grow complex for a long array of samples which is the case with Digital Audio. It is optimal to represent a short length of samples per Circuit when using the encode() method.

Working with Digital Audio

For faster processing of longer arrays, the stream method is preferred.

quantumaudio.stream(data)

It wraps the functions provided in the module quantumaudio.tools.stream that help process large arrays as chunks for efficient handling. Examples of its usage can be found in the Demos provided in the repository.

Running on Native Backends

A Scheme's decode() method uses local AerSimulator as the default backend. Internally, the function calls utils.execute() method that performs backend.run(). Any such backend object compatible with Qiskit can be passed to the backend= parameter of the decode() function. To configure this further or to use primitives, please refer to custom execute functions.

Running on External Quantum Backends

The package allows flexible use of Quantum Hardware from different Providers as the execution of circuits can be done independently. Depending on the results, there are two ways to decode quantum audio:

• Results Object: If the result obtained follow the format of qiskit.result.Result or qiskit.primitives.PrimitiveResult,
  • The audio can be decoded with scheme.decode_result(result_object) method.
  • In this case, relevant metadata information is automatically extracted and applied at decoding. It can also be manually passed using metadata= parameter.
    
    
• Counts Dictionary: If the result is in form of a counts dictionary or qiskit.result.Counts object,
  • The audio can be decoded using scheme.decode_counts(counts, metadata) method.
  • Here, the metadata dictionary is required which can be obtained from the encoded circuit's .metadata attribute.

Tip

Dictionaries are data type in python to store {key : value} pairs.

• Counts Dicitonary contains keys representing classical measurement outcomes and values indicating the number of times the outcome was observed. Example: {'00': 77, '01': 79, '10': 84, '11': 72}.
• Metadata Dictionary stores the key information that is required at decoding, which is commonly the original data dimensions to restore and layout of qubits. Both can be obtained from scheme.calculate() method.

Viewing Metadata

The Metadata Information can be viewed from the encoded circuit's .metadata attribute. The common keys found in a metadata are:

• num_samples (int) : Original sample length to restore.
• num_channels (int): Original number of channels to restore. (Applicable for multi-channel schemes)
• qubit_shape (tuple): Stores the arrangement and number of qubits that encode each aspect of the audio information i.e. Time, Channel (if applicable) and Amplitude.
  

The QPAM scheme's encoding only preserves num_samples (int) and the normalization factor - norm_factor (float) which is required to restore the values.

Note

When passing metadata manually in any of the decode functions, QPAM Scheme additionaly requires shots (int) information used for executing the circuit which can also be passed through the argument shots=.

Tip

The essential keys required for decoding with any scheme can be checked from the scheme's .keys attribute.

Using Custom Functions

The decode and stream operations can be configured with the following custom functions. They require few mandatory arguments followed by custom preceding keyword arguments (denoted as **kwargs).

• Process Function: The default process function of stream() simply encodes and decodes a chunk of data with default parameters. It can be overriden by passing a custom function to the process_function= parameter. The mandatory arguments for the custom process function are data= and scheme=.

processed_data = process_function(data, scheme, **kwargs)

• Execute Function : The default execute function for decode() can be overriden by passing a custom function to the execute_function= parameter. The mandatory argument for the custom execute function is circuit=. (QPAM also expects shots= since it's a metadata)

result = execute_function(circuit, **kwargs)

Example: An optional execute function is included in the package which uses Sampler Primitive: quantumaudio.utils.execute_with_sampler that can be passed to the decode() method. It requires the dependency pip install qiskit-ibm-runtime.

📘 Additional Resources

Notebook Examples

For examples of circuit preparation, signal reconstruction, and interactive demonstrations, please check the Demo Notebook. It combines the core package with additional functions from the demos/tools folder to go through Visual and Digital Audio examples.

Quick Export ⚡️

To quickly export quantumaudio from any audio file (e.g., mp3, ogg, flac, m4a), a script export.py is provided in the demos/scripts folder. Navigate to the directory and run:

python export.py -i path/to/input/audio/file

usage: export.py [-h] -i [-o] [-v] [--scheme] [--shots] [--sr] [--stereo] [--buffer_size]

Process quantum audio and export as .wav file.

options:
  -h, --help            show this help message and exit
  -i, --input           Path to the input audio file.
  -o, --output          Path to the output audio file. (default: saves in same directory with a prefix `qa_`)
  -v, --verbose         Enable verbose mode.
  --scheme              Quantum Audio Scheme (default: `qpam` for mono audio, `mqsm` for stereo audio).
  --shots               Number of shots for measurement (default: 8000)
  --sr                  Sample rate of Digital audio (default: 22050)
  --stereo              Enable stereo
  --buffer_size         Length of each audio chunk (default: 256)

Note

Digital Audio Dependencies must be installed to run this script.

🤝 Contributing

Contributions to Quantum Audio are welcome! This package is designed to be a versatile tool for both research and artistic exploration.

If you find any issues or have suggestions for improvements, please open an issue or submit a pull request on the GitHub repository.

• Code Contributions: Add new features, fix bugs, or improve existing functionality and code.
• Documentation: Enhance the README, tutorials, or other project documentation.
• Educational Use: If you’re using this project for learning, teaching or research, we’d love to hear about your experiences and suggestions.
• Feedback and Ideas: Share your thoughts, feature requests, or suggest improvements by opening an issue.

For more information on contributing to Code and Documentation, please review Contributing Guidelines

🚩 Future Releases

We're excited to keep the package updated with features and improvements! In future releases, we plan to introduce other schemes from Quantum Audio Literature along with Base Scheme Class Categories to support a generic structure for further contributions.

✅ Citing

If you use this code or find it useful in your research, please consider citing:

Moth Quantum and collaborators. (2024). Quantum Audio (v0.1.0). Zenodo. https://doi.org/10.5281/zenodo.14012135

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📧 Contact

We're here to help! If you have any questions or need further assistance, please feel free reach out to our team using the support options provided below:

• General Questions: Ask on Stack Overflow using the quantumaudio tag.
• Direct Contact: For private or specific issues, reach us at [email protected].
• Bugs & Feature Requests: Please open an issue on GitHub.

Before posting, check the Documentation, or existing questions in Stack Overflow to see if your question has been answered.

📜 Copyright

Copyright 2024 Moth Quantum

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.